MIKtlfY 

LIBRARY 

MNIVEISITY  Of 
CALIFOtNIA 


GIFT  OF 


GUIDE  TO  THE  MINERAL  COLLECTIONS  IN  THE 
ILLINOIS  STATE  MUSEUM 


STATE  OF  ILLINOIS 

FRANK  O.  LOWDEN,  GOVERNOR 

DEPARTMENT   OF    REGISTRATION   AND    EDUCATION 

FRANCIS   W.   SHEPARDSON,   PH.D.,   LL.D.,   DIRECTOR 


STATE  MUSEUM  DIVISION 

A.   R.   CROOK,    PH.D.,   CHIEF 
SPRINGFIELD 

BOARD  OF  MUSEUM  ADVISERS 

Administration  and  Fine  Arts: 

CHARLES   L.    HUTCHINSON,    A.M.,    Corn   Exchange   National 

Bank,  Chicago 
Botany: 

CHARLES  F.  MILLSPAUGH,  M.D.,  Field  Museum,  Chicago 
Ethnology: 

CHARLES  L.  OWEN,  A.B.,  Field  Museum,  Chicago 
Manufacturing  and  Business: 

EDWARD  W.  PAYNE,  State  Bank,  Springfield 
Zoology: 

HENRY  B.  WARD,  PH.D.,  University  of  Illinois,  Urbana 

A  FREE  INSTITUTION  FOR  THE  PEOPLE  : 

TO  PROMOTE   SCIENCE 

TO  PROMOTE   ART 

TO  PROMOTE   BUSINESS 

Hours: 

Week  Days:  8  A.M.  till  12  noon,  1:30  P.M.  till  5  P.M. 
Saturdays:  8  A.M.  till  3  P.M. 


LETTER  OF  TRANSMITTAL 

STATE  MUSEUM,  SPRINGFIELD 

August  31,  1919 
Francis  W.  Shepardson,  LL.D. 

Director,  Department  of  Registration  and  Education 

DEAR  SIR: 

For  the  purpose  of  increasing  the  usefulness  of  the  collections  in 
the  State  Museum  a  series  of  guidebooks  was  planned  a  few  years 
ago.  The  first  to  be  printed  was  the  General  Guide,  which  appeared 
in  1914  and  which  is  now  exhausted.  Herewith  is  submitted  a  Guide 
to  the  Mineral  Collections,  upon  which  the  chief  has  been  working  in 
moments  which  could  be  spared  from  other  work  for  the  past  several 
years. 

Hoping  that  it  may  prove  of  service  to  students  of  mineralogy 
and  also  to  those  visitors  whose  interest  is  of  a  general  character, 
I  am 

Yours  very  respectfully, 

A.  R.  CROOK, 

Chief,  State  Museum  Division 


GUIDE  TO  THE 

MINERAL  COLLECTIONS 

IN  THE 
ILLINOIS  STATE  MUSEUM  e 

V 


By 

A.  R.  CROOK,  PH.D. 

Chief,  State  Museum  Division,  Department  of 
Registration  and  Education 


SPRINGFIELD,  ILLINOIS 

1920 


Published  October  1920 


Composed  and  Printed  By 

The  University  of  Chicafco  Press 

Chicajo,  Illinois,  U.S.A. 


PREFACE 

In  the  following  pages  an  attempt  has  been  made  to  so  describe 
the  minerals  constituting  our  constantly  growing  collections  as  to 
emphasize  the  most  important  ones  and  at  the  same  time  to  present 
to  the  reader  a  good  idea  of  the  science  of  mineralogy.  The  average 
visitor  approaches  the  subject  as  a  child  would  and  just  as  the  human 
race  has  done.  When  early  man  wandered  up  stream  courses  and 
found  a  gold  nugget  he  doubtless  was  attracted  by  its  yellow  color, 
in  time  noticed  the  weight,  softness,  etc.,  and  learned  to  use  it  as  an 
ornament.  The  child  does  the  same,  using  the  senses  of  sight,  feel, 
taste,  and  smell  in  making  the  acquaintance  of  any  strange  sub- 
stance. Hence  the  physical  characteristics — form,  color,  hardness, 
and  weight — of  various  minerals  are  described,  and  then  their  chemi- 
cal constituents,  geological  and  geographical  relations,  and  use  are 
given.  By  becoming  acquainted  with  various  minerals  the  visitor 
obtains  a  knowledge  of  the  science. 

In  preparation  of  this  work  the  writer  has  used  chiefly  Dana's, 
Mier's,  Lacroix's,  and  Tschermak's  mineralogies  and  Tutton's  and 
Groth's  crystallographies,  in  addition  to  individual  articles  in 
U.S.G.S.  reports,  scientific  journals,  etc. 

Especial  thanks  are  due  Professor  O.  C.  Farrington  for  painstak- 
ing revision  of  the  manuscript,  Professor  W.  S.  Bayly  for  careful 
reading  of  the  proof,  and  the  University  of  Chicago  Press  for  the 
thorough  manner  in  which  their  part  of  the  work  has  been  done. 

Professor  Farrington  supplied  photographs  for  Plates  IV,  XVIII, 
XlXa,  and  XXVIIa.  Plate  VIb  is  after  W.  M.  Foote,  and  Plate  la 
is  reproduced  by  permission  of  B.  F.  Buck  &  Co.  The  other  illus- 
trations are  by  the  writer. 

A.  R.  CROOK 

August,  1919 


43927; 


IX 


TABLE  OF  CONTENTS 


LIST  OF  ILLUSTRATIONS •     •  xi" 

ABBREVIATIONS ......  xxi 

INTRODUCTION .    ...    .     .     .     .  i 

CLASS    I.  ELEMENTS    .     .     .'.-..     .......     .     .     .  5 

LIST  OF  ELEMENTS  AND  THEIR  ATOMIC  WEIGHTS    .     .    V    .     .     .  45 

CLASS      II.  SULPHIDES .,  .  -  .  46 

CLASS      III.    SULPHANTIMONITES,  SULPHARSENITES          ...'..  68 

CLASS     IV.  HALOIDS ...     .  76 

CLASS       V.  OXIDES      ....'.,.,..,...  82 

CLASS     VI.  CARBONATES  .     .     .     .     ...     .     .     .     .     .     .  112 

CLASS    VII.  SILICATES .  132 

CLASS  VIII.  NIOBATES,  TANTALATES 175 

CLASS     IX.  PHOSPHATES,  ETC '. 175 

CLASS      X.  BORATES,  URANATES      .     i     ...     ...     .     .  177 

CLASS     XL  SULPHATES,  CHROMATES,  TELLURATES      .     ....     .  179 

CLASS    XII.   TUNGSTATES,  MOLYBDATES 185 

CLASS  XIII.  ORGANIC  ACID  SALTS 187 

CLASS  XIV.  HYDROCARBONS 187 

SUMMARY 194 

NAMES  OF  MINERALS ....;..     ...  196 

THE  USES  OF  MINERALS .     ....     ...     .  197 

HISTORY  OF  THE  STUDY  OF  MINERALS      ..».....".  198 

LIST  OF  MINERALS 202 

INDEX 279 


XI 


LIST  OF  ILLUSTRATIONS 

PAGE 

FIG.  i.  MODEL  OF  OCTAHEDRON;  PREVAILING  OUTLINE  OF  DIA- 
MOND .  .  , ;  . 5 

FIG.    2.    AXES     .     ..."     /    .;'*     . 6 

FIG.    3.    METHOD  OF  CONSTRUCTING  CRYSTALLOGRAPHIC  AXES        .  7 

FIG.   4.    CONSTRUCTION  OF  AN  OCTAHEDRAL  PLANE    ....  7 

FIG.    5.    COMPLETED  OCTAHEDRON  .       .       ...       .       .       .  8 

FIG.    6.    MODEL  OF  TRAPEZOHEDRON     .       .       .       ...       .  9 

FIG.    7.    COMPLETED  TRAPEZOHEDRON  .              9 

FIG.    8.    MODEL  OF  TRISOCTAHEDRON    .       -. 10 

FIG.    9.    TRISOCTAHEDRON  COMPLETED  .......  10 

FIG.  10.    MODEL  OF  HEXOCTAHEDRON    . 12 

FIG.  ii.    HEXOCTAHEDRON  COMPLETED 12 

FIG.  12.  GROWTH  OF  UNSHADED  PLANES  OF  THE  WOODEN  OCTA- 
HEDRON PRODUCE  THE  GLASS  TETRAHEDRON  COVER- 
ING IT  .  .  .  . 12 

FIG.  13.    RIGHT-HANDED  TETRAHEDRON 12 

FIG.  14.    WOODEN  OCTAHEDRON  INCLOSED  BY  GLASS  TETRAHEDRON  13 

FIG.  15.    LEFT-HANDED  TETRAHEDRON 13 

FIG.  16.    INTERPENETRATING       SUPPLEMENTARY      TETRAHEDRONS 

(TETRAHEDRAL  TWINS) 13 

FIG.  17.    TETRAHEDRAL  TWIN  WITH  CORNERS  TRUNCATED      .         .  14 

FIG.  18.    MODEL  OF  RIGHT-HANDED  HEXATETRAHEDRON    .       .       .  15 

FIG.  19.    CONSTRUCTION  OF  HEXATETRAHEDRON 15 

FIG.  20.    INTERPENETRATING  TRUNCATED  TETRAHEDRONS  BEVELED 

BY  HEXATETRAHEDRONS    .       .       .       .       .       .       .  16 

FIG.  21.    MODEL  OF  "SPINEL  TWIN"  .   .       .    ..j.*!...,;..    "...  '  17 

FIG.  22.    DRAWING  OF  SPINEL  TWIN       .      .    ,','•"    .       ...  17 

FIG.  23.    Two  KINDS  OF  AXES  OF  SYMMETRY        .       .       .      '.     ' .  18 
FIG.  24.    DOTTED  LINES  SHOW  DIRECTION  OF  PLANES  OF  SYMMETRY 

IN  CUBE 19 

FIG.  25.    ANGLES  OF  INCIDENCE  AND  REFRACTION       .       .       .       .  19 

FIG.  26.    MODEL  OF  ORTHORHOMBIC  BrpYRAMio   .       .       .       .  25 

FIG.  27.    ORTHORHOMBIC  PYRAMIDAL  PLANE  AND  AXES      .       ...  25 

FIG.  28.    OBTUSE  BIPYRAMID  CHARACTERISTIC  OF  SULPHUR       .       .  26 

FIG.  29.    MODEL  OF  BRACHYDOMES  AND  MACROPINACOIDS         .       .  26 

FIG.  30.    UPPER  BRACHYDOME  PLANES    .       ....:*       .       .  26 

FIG.  31.    MODEL  OF  MACRODOMES  AND  BRACHYPINACOIDS  .       .      v  27 

FIG.  32.    UPPER  MACRODOMES    .     .      -,,,„,..»      v.  ,.,,*.  ,v  27 

xiii 


xiv  LIST  OF  ILLUSTRATIONS 

PAGE 

FIG.  33.  PRISM  AND  BASAL  PLANES 27 

FIG.  34.  BASE,  MACROPINACOID,  AND  BRACHYPINACOID      ...  28 

FIG.  35.  MODEL  or  BASE,  MACRO-  AND  BRACHYPINACOID  ...  28 

FIG.  36.  MODEL  OF  PRISM,  BRACHYPINACOID,  AND  BRACHYDOME      .  28 

FIG.  37.  RIGHT-HANDED  SPHENOID  .       .     .> 28 

FIG.  38.  SULPHUR,  USUAL  HABIT    .       . 29 

FIG.  39.  SULPHUR,  SPHENOIDAL  HABIT  .       .       .       .       .     ,,       .  29 

FIG.  40.  AXES  or  MONOCLINIC  CRYSTAL       .       .....  30 

FIG.  41.  CUBE     .       .       .       .       .       ...       ...       .  33 

FIG.  42.  TETRAHEXAHEDRON  MODEL       .     .       ....       .  35 

FIG.  43.  CONSTRUCTION  OF  TETRAHEXAHEDRON 35 

FIG.  44.  MODEL  OF  A  DODECAHEDRON 39 

FIG.  45.  CONSTRUCTION  OF  A  DODECAHEDRON 40 

FIG.  46.  STIBNITE  CRYSTAL      ....       .       .       .       .       .       .  47 

FIG.  47.  CUBE  TRUNCATED  BY  OCTAHEDRON        .      ....       .  49 

FIG.  48.  MODEL  OF  CUBE  TRUNCATED  BY  OCTAHEDRON     ...  49 

FIG.  49.  GALENA,  Jo  DAVIESS  COUNTY,  ILLINOIS        .       .       .       .  50 

FIG.  50.  MODEL  OF  PLANES  APPEARING  ON  GALENA         *  50 

FIG.  51.  TWIN  LAMELLAE  IN  GALENA    .       .       .      *.       .       .       .  51 

FIG.  52.  SPHALERITE         .       »       .       .       .       .       .      ..     .*      .  53 

FIG.  53.  MODEL  OF  THREE-FACED  TETRAHEDRON,  A  TRISTETRAHEDRON  54 

FIG.  54.  CONSTRUCTION  OF  TRIGONAL  TRISTETRAHEDRON  .      .       .  54 

FIG.  55.  SPHALERITE        Y      /  .  .       .       .       .       .       .       .       .  54 

FIG.  56.  ACUTE  PRIMARY  BIPYRAMTD     .......       .  57 

FIG.  57.  OBTUSE  PRIMARY  BIPYRAMTD    .       ...      .       .       .       .       .  57 

FIG.  58.  MODEL  OF  SECONDARY  BIPYRAMID  .       .       »       .     -. .       .  58 

FIG.  59.  DITETRAGONAL  BIPYRAMID       .......       .       .  58 

FIG.  60.  MODEL  OF  DITETRAGONAL  BIPYRAMID    .       .       .       .       .  58 

FIG.  61.  PRIMARY  PRISM 59 

FIG.  62.  SECONDARY  PRISM      .       .       .       .       .       .       ....  59 

FIG.  63.  MODEL  OF  DITETRAGONAL  PRISM 59 

FIG.  64.  COMBINATION  OF  PRIMARY  PRISM,  SECONDARY  PRISM,  SEC- 
ONDARY BIPYRAMID,  AND  DITETRAGONAL  BIPYRAMID  59 

FIG.  65.  MODEL  OF  BISPHENOID .60 

FIG.  66.  CHALCOPYRITE 60 

FIG.  67.  CHALCOPYRITE,  FRENCH  CREEK,  PENNSYLVANIA  ...  60 

FIG.  68.  CHALCOPYRITE,  NEUDORF 61 

FIG.  69.  PYRITOHEDRON  DERIVED  BY  DISAPPEARANCE  OF  TETRA- 
HEXAHEDRAL  PLANES  DARKENED,  AND  GROWTH  OF  THE 

OTHER  PLANES 62 

FIG.  70.  MODEL  OF  A  DIPLOID        . 62 

FIG.  71.  MODEL  OF  COMBINATION  OF  PYRITOHEDRON  AND  CUBE      .  63 


LIST  OF  ILLUSTRATIONS  XV 

PAG3 

FIG.   72.    MARCASITE        .       .       .       .       .       ._-'-'.•*•.    .       .       .  64 

FIG.    73.    MARCASITE        .....    "  .       •       ...  64 

FIG.    74.     "  SPEARHEAD  PYRITES  "    .       .       .       /      .       ;       .       .  65 

FIG.    75.    "  COCKSCOMB  PYRITES  "   .       ...     .       .>  .     ^.       .  65 

FIG.    76.    ARSENOPYRITE  .       .       .:      .       .       .       .    ~\       .'     .  67 

FIG.    77.    ARSENOPYRITE  .       .       .       .       .       .       .'       ...  67 

FIG.    78.    SYMMETRY  PLANES  OF  A  DITRIGONAL  POLAR  CRYSTAL      .  68 

FIG.    79.    AXES  OF  HEXAGONAL  SYSTEM    -    .       .       .     ".       .-    .  68 

FIG.    80.    MODEL  OF  PRIMARY  PYRAMID        ....       .       .  69 

FIG.    81.    BASAL  SECTION  SHOWING  RELATION  OF  PRIMARY,  SECOND- 
ARY, AND  DlHEXAGONAL  PYRAMIDS  AND  PRISMS    .          .  69 
FlG.     82.      MODEL  OF  DlHEXAGONAL  BlPYRAMID    .....        ...          .  69 

FIG.    83.    MODEL  OF  PRIMARY  HEXAGONAL  PRISM      .:     .       *       .  .  70 

FIG.    84.    SECONDARY  HEXAGONAL  PRISM      ...       .       .       .  70 

FIG.    85.    MODEL  OF  DIHEXAGONAL  PRISM   .,    .„       .       .       .       .  70 

FIG.    86.    RHOMBOHEDRON   RESULTING   FROM   DISAPPEARANCE   OF 
DARKENED    PLANES    OF   THE    INTERIOR    FIGURE — 

HEXAGONAL  BIPYRAMTD  .       ...       .       .       .  71 

FIG.    87.    MODEL  OF  POSITIVE  SCALENOHEDRON  .       .       .       .       .  71 

FIG.    88.    MODEL  OF  SCALENOHEDRON   TRUNCATED   BY   RHOMBO- 
HEDRON    .       ....       .       .       .       .       .  71 

FIG.    89.    MODEL  OF  TRUNCATED  PRISM       ....       .       .  71 

FIG.    90.    PYRARGYRITE,  CRYSTAL  FORM       .       .       .       .       .       .  72 

FIG.    91.    PREVAILING  FORM  OF  TETRAHEDRITE   .       .       .       .       .  73. 

FIG.    92.    CHARACTERISTIC  FORM  OF  TETRAHEDRITE   .       .       .       .  73; 

FIG.    93.    TENNANTITE  (SCHWATZITE)     ...       .       .       .       .  74. 

FIG.    94.    MODEL  OF  SANDBERGERITE  .         .       ,       „       ,       .       .  74 

FIG.    95.    HALITE  CUBE  FROM  SALT  BRINE  ,.       .  ^  ,. .,     .       .       .  77 

FIG.    96.    FLUORITE 78 

FIG.    97.    FLUORITE .  78- 

FIG.    98.    MODEL  OF  FLUORITE  TWIN 79, 

FIG.    99.    QUARTZ;  PRISM  AND  RHOMBOHEDRON 83, 

FIG.  100.    QUARTZ       .       .      v .  83 

FIG.  101.    A  FORM  OF  QUARTZ  COMMON  AT  ALSTON  MOOR,  ENGLAND  83 

FIG.  102.    QUARTZ '.    ,   .    ;  ..    ,.       .  83 

FIG.  103.    QUARTZ;  POSITIVE  LEFT  TRIGONAL  TRAPEZOHEDRON        .  84 

FIG.  104.    QUARTZ;  POSITIVE  RIGHT  TRIGONAL  TRAPEZOHEDRON      .  84 

FIG.  105.    Two  RIGHT-HANDED  QUARTZ  CRYSTALS  TWINNED     .       .  85 
FIG.  106.    BRAZIL    TWIN;     RIGHT-    AND    LEFT-HANDED    QUARTZ 

CRYSTALS  INTERPENETRATING        .              .       .       .85. 
FIG.  107.    BRAZIL  TWIN.    Two  RIGHT-HANDED  CRYSTALS  JUXTA- 
POSED    86 

FIG.  108.    QUARTZ;  BOURG  DE  OISANS  TWIN  86 


xvi  LIST  OF  ILLUSTRATIONS 

PAGE 

FIG.  109.    QUARTZ  ETCHED  WITH  HYDROFLUORIC  ACID;    A,  LEFT- 
HANDED;  B,  RIGHT-HANDED 86 

FIG.  no.    AIRY'S  SPIRAL  IN  RIGHT-HANDED  CRYSTAL  .       ...  88 

FIG.  in.    CUPRITE 92 

FIG.  112.    ZINCITE      .       .       .       .       .       .     •*.       .     •:.       .       .  93 

FIG.  113.    CORUNDUM        . .'      .       .  94 

FIG.  114.    CORUNDUM        .       . 95 

FIG.  115.    CORUNDUM  WITH  TWINNING  LAMELLAE  PARALLEL  TO  R  .  95 

FIG.  116.    CROSS-SECTION  OF  DICHROSCOPE   .       .       .      ...    ,  ..       .  96 

FIG.  117.    DIRECTION  OF  VIBRATION  OF  Two  RAYS  OF  LIGHT  PASSING 

THROUGH  CALCITE  PRISM        .       .       .       .       .       .96 

FIG.  118.     RUBY  .        .       .       ;       . 97 

FIG.  119.    SAPPHIRE    .       .....       .       ....  97 

FIG.  1 20.    MODEL  OF  RHOMBOHEDRON    .    '  .       .       .     ..       .       .  98 

FIG.  121.    HEMATITE 99 

FIG.  122.    TABULAR  HEMATITE  CRYSTAL  TWINNED  PARALLEL  TO  THE 

PRISM  .       .    y       .       .       .       .       .       .       .       .99 

FIG.  123.    MANGANITE       ,       .       .       ...       /     .       .       .  100 

FIG.  124.    MANGANITE       '.  •    .       .       .       ..-.,..  100 

FlG.  125.      GOETHITE     .          .          .  .          .          .         ..          .          .          »          .       102 

FIG.  126.  GOETHITE   .       .....       .       .       .      v      .       .       .     102 

FIG.  127.  SPINEL  TWIN     .       . .    '1       .       .       ....       .     105 

FIG.  128.  SPINEL        .-    ,      .       .       .       .       .'    .       .       .       .105 

FIG.  129.  MAGNETITE       .       ,       .       .       .       .       .       .       .       .     106 

FIG.  130.  CASSITERITE      ....       ...       .       .       .       .       .     108 

FIG.  131.  CASSITERITE      .       .       .       .       .       .       .       .       .       .108 

FIG.  132.  RUTILE       ,       .       .'......       .       .       .109 

FIG.  133.  RUTILE  TRIPLET no 

FIG.  134.  RUTILE  OCTET no 

FIG.  135.  CALCITE.    POSITIVE  RHOMBOHEDRON;  CLEAVAGE  RHOM- 
BOHEDRON .       .       .       ...       .       .       .     '.     113 

FIG.  136.  CALCITE.    NEGATIVE  RHOMBOHEDRON        .       .       .       .113 

FIG.  137.  CALCITE.    NEGATIVE  ACUTE  RHOMBOHEDRON    .       .       .114 

FIG.  138.  CALCITE,  SCALENOHEDRON 114 

FIG.  139.  CALCITE,  PRISM  AND  NEGATIVE  OBTUSE  RHOMBOHEDRON      114 
FIG.  140.  CALCITE,  SHOWING  PRISM,  NEGATIVE  OBTUSE  RHOMBO- 
HEDRON, AND  BASE  -.  '    .       .     114 

FIG.  141.  CALCITE;  COMBINATION  OF  SCALENOHEDRON  AND  RHOM- 
BOHEDRON .       .       .       .       .      ,';      ...       .     114 

FIG.  142.  CALCITE  RHOMBOHEDRON       ....       .       .       :      .     114 

FIG.  143.  CALCITE  SCALENOHEDRON       ...       .       .       .  115 

FIG.  144.  CALCITE  SCALENOHEDRON 115 


LIST  OF  ILLUSTRATIONS  xvii 

PAGE 

FIG.  145.    CALCITE  PRISM .       .       .       .  115 

FIG.  146.    CALCITE  SCALENOHEDRON       .       .       .    ~  .  '    .       .       .  116 

FIG.  147.    CALCITE  SCALENOHEDRON       .       .    -  .       .       ...       .  116 

FIG.  148.    CALCITE  ETCHED  WITH  DILUTE  HYDROCHLORIC  ACID        .  118 

FIG.  149.    DOLOMITE  ETCHED  WITH  DILUTE  HYDROCHLORIC  Aero     .  118 

FIG.  150.    ELASTICITY  COEFFICIENT  or  CALCITE   .       .       .       .       .  119 

FIG.  151.    ELASTICITY  COEFFICIENT  OF  DOLOMITE        .       .       .       .119 

FIG.  152.    GLIDE  PLANES  IN  CALCITE      .       .       .       .       .       .       .  119 

FIG.  153.    ARAGONITE.       .....       .       ..      .       .       .       .123 

FIG.  154.    BASAL  SECTION  OF  ARAGONITE  TRIPLET       .       /     .       .  124 

FIG.  155.    B ASAL  SECTION  OF  ARAGONITE;  INTERPENETRANT  TRIPLET  124 
FIG.  156.    WITHERITE        .       .       ...       .       .       ...       .125 

FIG.  157.     CROSS-SECTION  OF  WITHERITE       .       .       ....       .  125 

FIG.  158.    CERUSSITE         .       .       .-     .       .       .       .       .       .       .  127 

FIG.  159.    CERUSSITE "    .       .       .       .       .  127 

FIG.  1 60.    THREE  CERUSSITE   CRYSTALS  INTERPENETRATING   PAR- 
ALLEL TO  PRISM  PLANES  .       .      v      ;.       .       .       .  127 

FIG.  161.    AXES  OF  MONOCLINIC  CRYSTAL     .     ...       .  '    .       .       .  128 

FIG.  162.    MONOCLINIC  BIPYRAMID  .       .       .       .       .     •  •    *  •       •  129 

FIG.  163.    ORTHODOMES  AND  CLINODOMES      .       .'-...  .       .       .  129 

FIG.  164.    MODEL  OF  PRISM  AND  BASAL  PLANE    .       .       .       .       .  130 

FIG.  165.    MALACHITE  SECTION        ..      ....       ...       .  130 

FIG.  1 66.    AZURITE  CRYSTAL,  SHOWING  ALSO  POSITION  OF  OPTIC  AXES 

AND  AXIAL  PLANE 131 

FIG.  167.    MODEL  OF  AN  ORTHOCLASE  CRYSTAL    ...       .       .  134 

FIG.  1 68.    ORTHOCLASE      .       .  '    .       .       .       .       .    "• .       .       .  134 

FIG.  169.    ADULARIA  ORTHOCLASE    .       .       .       .       ...       .  134 

FIG.  170.    MODEL  OF  CARLSBAD  TWIN,  INTERPENETRATING      .       .  134 

FIG.  171.    BAVENO  TWIN,  COMPOSITION  FACE       .       .       ....  134 

FIG.  172.    MANEBACH  TWIN,  COMPOSITION  FACE         .       .       .       .134 

FIG.  173.    ORTHOCLASE  SECTION;  AXIAL  PLANE,  ANGLE  OF  EXTINC- 
TION      135 

FIG.  174.    ORTHOCLASE  (ADULARIA);  AXIAL  PLANE     .       .       .  -.  .  136 
FIG.  175.    ORTHOCLASE;    POSITIVE  AND  NEGATIVE  DIRECTION  OF 

EXTINCTION 136 

FIG.  176.    TRICLINIC  AXES  OF  COPPER  SULPHATE;    No  AXES  AT 

RIGHT  ANGLES  .       .       . 139 

FIG.  177.    ALBITE       .       .       .       .      :.       .      *       ...       .  140 

FIG.  178.    ALBITE,  SHOWING  ALBITE  LAW      .,    V      .       .       .       .  140 

FIG.  179.    ALBITE,  PERICLINE  TWIN       .       .       .       .     ,.       .       .  141 

FIG.  1 80.    ALBITE;  AXIAL  PLANE .       .  141 

FIG.  181.    ALBITE  SECTION .  141 


xviii  LIST  OF  ILLUSTRATIONS 


PAGE 


FIG.  182.  ALBITE  SECTION .  .  .141 

FIG.  183.  RHOMBIC  SECTION  OF  ANORTHITE ,142 

FIG.  184.  ANORTHITE,  SHOWING  POSITION  OF  AXIAL  PLANE  AND 

BISECTRIX 142 

FIG.  185.  MICROSCOPIC  SECTION  OF  LEUCITE  BETWEEN  CROSSED 

NICOLS  .  .  ? 145 

FIG.  i860.  DIOPSIDE  .  .  .  ,  .  '. 147 

FIG.  1 86ft.  PHOTOGRAPH  OF  DIOPSIDE  FROM  CANTLEY,  QUEBEC, 

CANADA  .  .  .  .....  .  .  .  147 

FIG.  187.  DIOPSIDE ......  v  7  •*  •  148 

FIG.  1 88.  DIOPSIDE,  SHOWING  OPTIC  AXES,  ACUTE  BISECTRIX,  AXES 

OF  ELASTICITY 148 

FIG.  189.  AUGITE  ....  .  .  .  .  .  .  .  148 

FIG.  190.  AUGITE  TWIN  . 148 

FIG.  191.  AUGITE  CROSS-SECTION  PERPENDICULAR  TO  PRISM  PLANES  149 
FIG.  192.  ENSTATITE,  SHOWING  PARALLEL  EXTINCTION  .  .  .  149 
FIG.  193.  DIOPSDDE,  SHOWING  OBLIQUE  EXTINCTION  ANGLE  .  .149 

FIG.  194.  RHODONITE .  .151 

FIG.  195.  ANTHOPHYLLITE,  AXIAL  PLANE  AND  OPTIC  AXES  .  .152 

FIG.  196.  HORNBLENDE 154 

FIG.  197.  HORNBLENDE  ..  ...'..'•;..'.'.' 154 

FIG.  198.  HORNBLENDE  SECTION  PERPENDICULAR  TO  PRISM  .  .154 
FIG.  199.  HORNBLENDE  ,  i, ".-...  r'  '.  .  ,  '.  .  .  154 
FIG.  200.  ANTHOPHYLLITE;  PARALLEL  EXTINCTION  .  .  .  .155 

FIG.  201.  TREMOLITE;  EXTINCTION  ANGLE 155 

FIG.  202.  HORNBLENDE;  EXTINCTION  ANGLE 155 

FIG.  2030.  PHOTOGRAPH  OF  BERYL  FROM  BRAZIL 157 

FIG.  2036.  BERYL        ....       .       .       .       .    "•  .       .    •  ..       .     157 

FIG.  204.    GARNET      .       .       ...       .       .       ....       .       .       .     158 

FIG.  205.  GARNET  .  .  ,t  .  .  .  .  .  .  .  .  .  159 

FIG.  206.  GARNET  .  .... 159 

FIG.  207.  ZIRCON 161 

FIG.  208.  ZIRCON  ...  •  . 161 

FIG.  209.  TOPAZ 162 

FIG.  210.  TOPAZ,  SHOWING  OPTIC  AXES  AND  AXIAL  PLANE  .  .  162 

FIG.  211.  TOURMALINE 164 

FIG.  212.  TOURMALINE 164 

FIG.  213.  TOURMALINE,  ANALOGOUS  END  .  .  .  . '  .  .165 
FlG.  214.  FOUR-TWINNED  CRYSTALS  OF  STILBITE  ....  l66 

FIG.  215.  STILBITE  SHEAF 166 

FIG.  216.  LEUCITE 167 

FIG.  217.  NATROLITE 168 


LIST  OF  ILLUSTRATIONS  xix 

PAGE 

FIG.  218.  MUSCOVITE  .  .  .'  .  .  .  :  .  .  .  169 
FIG.  219.  MUSCOVITE:  PRESSURE  FIGURE,  PERCUSSION  FIGURE, 

OPTIC  AXES  .  .  .  .  ...  .  .169 

FIG.  220.  BIOTITE;  AXIAL  PLANE 171 

FIG.  221.  BASAL  SECTION  OF  BIOTITE,  SHOWING  POSITION  OF  AXIAL 

PLANE  AND  PERCUSSION  FIGURE 171 

FIG.  222.  APATITE  ,  .  ,.  .  ;  >  .  * .  .  .  .  .  .  175 

FIG.  223.  BARITE  ...  . 179 

FIG.  224.  BARITE  .  .  * 179 

FIG.  225.  BARITE 179 

FIG.  226.  CELESTITE 180 

FIG.  227.  ANGLESITE 181 

FIG.  228.  ANGLESITE 181 

FIG.  229.  GYPSUM  .  .  .  *  ,  .  •  .  •  •  •  •  •  ^2 

FIG.  230.  GYPSUM  .  .  .  . 182 

FIG.  231.  GYPSUM  „  .  . 182 

FIG.  232.  GYPSUM  TWINNED  BY  JUXTAPOSITION 183 

FIG.  233.  GYPSUM,  TWINNED  BY  INTERPENETRATION  .  .  .183 

FIG.  234.  WOLFRAMITE 185 

FIG.  235.  WULFENITE 186 

FIG.  236.  WULFENITE  . .  . 186 


PLATE  I.  a,  PREVAILING  FORMS  OF  THE  DIAMOND.  G.  F.  WILLIAMS  COL- 
LECTION; b,  GLASS  MODEL  OF  CULLINAN  DIAMOND,  THE  LARGEST 
DIAMOND  EVER  FOUND. 

PLATE  II.    CONSTRUCTION  OF  RIGHT-HAND  UPPER  OCTANT  OF  TRISOCTA- 

HEDRON  ABOVE  AND  OF  TRAPEZOHEDRON  BELOW. 

PLATE  III.    CONSTRUCTION  OF  ONE  OCTANT  OF  HEXOCTAHEDRON. 

PLATE  IV.  DENDRITIC  COPPER  FROM  CALUMET  AND  HECLA  MINING 
REGION,  MICHIGAN. 

PLATE  V.  MUKEROP  METEORITE,  ONE-SIXTH  NATURAL  SIZE.  FELL  IN 
AMALIA-GOAMUS,  WEST  AFRICA. 

PLATE  VI.  a,  STIBNITE,  JAPAN;  b,  MOLYBDENITE  FROM  ALDFIELD, 
PONTIAC  COUNTY,  QUEBEC,  CANADA. 

PLATE  VII.  a,  GROUP  OF  PYRITE  CUBES,  SHOWING  STRIATIONS,  CENTRAL 
CITY,  COLORADO;  b,  PYRITE.  A  PYRITOHEDRON  AND  CUBES,  COLO- 
RADO. 

PLATE  VIII.    MARCASITE,  Jo  DAVIESS  COUNTY,  ILLINOIS. 

PLATE  IX.  MARCASITE  DISKS,  GULF  MINE,  SPARTA,  RANDOLPH  COUNTY, 
ILLINOIS. 


xx  LIST  OF  ILLUSTRATIONS 

PLATE  X.    MARCASITE,  SHOWING  RADIATED  INTERNAL  STRUCTURE. 

PLATE  XL  MARCASITE  COATING  GALENA,  MARSDEN  MINE,  Jo  DAVIESS 
COUNTY,  ILLINOIS. 

PLATE  XII.  FLUORITE  GROUP  FROM  ROSICLARE,  HARDIN  COUNTY, 
ILLINOIS. 

PLATE  XIII.  a,  FLUORITE  CUBES,  ROSICLARE,  ILLINOIS;  b,  OCTAHEDRONS 
CLEAVED  OUT  BY  TEN- YEAR-OLD  BOY,  SHOWING  EASE  AND  REGU- 
LARITY OF  CLEAVAGE. 

PLATE  XIV.  a,  SMOKY  QUARTZ,  "CAIRNGORM,"  FROM  MONTANA; 
b,  QUARTZ,  MONTGOMERY  COUNTY,  ARKANSAS. 

PLATE  XV.    QUARTZ  GROUP,  MONTGOMERY  COUNTY,  ARKANSAS. 

PLATE  XVI.  QUARTZ,  "BOURG  DE  OISANS"  TWIN,  HOT  SPRINGS, 
ARKANSAS. 

PLATE  XVII.    AMETHYST,  THUNDER  BAY,  LAKE  SUPERIOR. 

PLATE  XVIII.    Moss  AGATE,  INDIA. 

PLATE  XIX.  a,  BOTRYOIDAL  HEMATITE,  CUMBERLAND,  ENGLAND; 
b,  LIMONITE,  HARDIN  COUNTY,  ILLINOIS. 

PLATE  XX.    CALCITE,  WEBB  CITY,  MISSOURI. 

PLATE  XXI.  a,  CALCITE,  "DOG-TOOTH  SPAR,"  JOPLIN,  MISSOURI; 
b,  CALCITE,  "ICELAND  SPAR,"  SHOWING  DOUBLE  REFRACTION. 

PLATE  XXII.    CALCITE,  JOPLIN,  MISSOURI. 

PLATE  XXIII.  CALCITE  SCALENOHEDRON,  ROSSIE,  ST.  LAWRENCE 
COUNTY,  NEW  YORK. 

PLATE  XXIV.  a,  CALCITE,  JOPLIN,  MISSOURI;  b,  QUARTZ  GEODE  WITH 
LARGE  FLAT  RHOMBOHEDRAL  CRYSTALS,  ST.  FRANCISVTLLE,  MISSOURI. 

PLATE  XXV.  a,  ARAGONITE  CRYSTALS  FOUR  INCHES  IN  DIAMETER, 
CIANCIANA,  SICILY;  b,  STALACTITES,  BISBEE,  ARIZONA. 

PLATE  XXVI.  a,  MICROCLINE,  "AMAZON  STONE,"  PIKE'S  PEAK,  COLO- 
RADO; b,  MICROCLINE,  PIKE'S  PEAK,  COLORADO. 

PLATE  XXVII.  a,  GARNETS;  DODECAHEDRON  FROM  SALIDA,  COLORADO, 
TRAPEZOHEDRON  FROM  NORTH  CAROLINA,  AND  COMBINATION  FROM 
FORT  WRANGEL,  ALASKA;  b,  A  DODECAHEDRON  NEARLY  FOUR  INCHES 
IN  DIAMETER  FROM  SALIDA,  COLORADO. 

PLATE  XXVIII.  a,  TOURMALINE  DOUBLY  TERMINATED;  VARIOUSLY 
COLORED  CRYSTAL  FROM  MESA  GRANDE,  CALIFORNIA;  b,  BLACK, 
WELL-CRYSTALLIZED  SPECIMEN  FROM  HADDAM,  CONNECTICUT. 

PLATE  XXIX.  a,  APATITE,  RENFREW,  CANADA;  b,  BARITE,  ALSTON 
MOOR,  ENGLAND. 

PLATE  XXX.    GYPSUM,  SHOWING  FISHTAIL  TWIN  AND  CURLED  FORM. 

PLATE  XXXI.    GYPSUM,  "SELENITE,"  WAYNE  COUNTY,  UTAH. 


ABBREVIATIONS 

a,  b,  c  =  Crystallographic  axes 

a,  b,  C  =  Direction  of  greatest,  medium,  and  least  elasticity 

a,  j8,  7  =  Greatest,  medium,  and  least  index  of  refraction 

a,  j8,  7  =  Angles  between  crystallographic  axes 

e  =  Direction  of  the  extraordinary  ray  or  its  index  of  refraction 

2  E  =  Apparent  value  of  axial  angle  in  the  air 

7—  a  =  Maximum  biref raction 

2  H  =  Value  of  axial  angle  when  mineral  is  immersed  in  oil 

n  =  Index  of  refraction 

p  =  Axial  angle  of  red  light 

2  V  =  True  value  of  angle  between  optic  axes 

v  =  Axial  angle  of  violet  (blue)  light 

co  =  Index  of  refraction  of  the  ordinary  ray 


XXI 


INTRODUCTION 

Minerals  play  a  large  part  in  the  annual  increase  in  wealth  and 
in  the  comfort  of  the  inhabitants  of  Illinois.  The  state  is  not  usually 
thought  of  as  a  mineral-producing  region,  as  is  Colorado,  Montana,, 
or  California,  and  the  fact  is  not  usually  known  that  the  money 
value  of  the  minerals  obtained  in  this  state  exceeds  that  of  any 
state  west  of  the  Mississippi  River. 

But  such  is  the  case.  During  the  year  preceding  the  world- war 
the  total  value  of  mineral  products  in  Illinois  amounted  to  more 
than  one  hundred  and  seventeen  millions  of  dollars,  while  that  of 
California,  the  nearest  competitor,  was  only  one  hundred  and  one 
millions,  and  Colorado  and  Montana  together  fell  even  farther  be- 
hind Illinois  in  mineral  production. 

The  use  of  minerals  is  an  index  of  civilization.  Man  is  the  only 
member  of  the  animal  kingdom  to  utilize  minerals;  and  the  more 
primitive  his  place  in  human  society,  the  less  does  he  do  so. 

The  whole  fabric  of  civilization  depends  upon  iron,  copper,  gold, 
and  other  metals,  and  upon  coal,  building  stone,  and  clays.  The 
people  of  our  state  produce  some  of  these  substances  in  great  quan- 
tities and  use  all  kinds  of  minerals  from  all  corners  of  the  globe. 

Some  minerals  occur  in  extensive  deposits  in  the  state,  others  are 
scattered  here  and  there.  The  majority  of  those  described  in  the 
following  pages  have  been  found  within  the  region  and  many  of  the 
others  are  very  useful  for  our  people. 

While  more  than  a  thousand  different  minerals  are  known,  only 
about  one  hundred  are  common  enough  to  claim  our  special  attention. 
These  one  hundred  are  well  illustrated  in  the  museum  collections. 

Many  visitors,  while  having  a  general  idea  of  the  subject,  are 
unable  to  say  just  what  a  mineral  is.  Upon  investigation  they 
learn  that  a  mineral  is  a  natural,  inorganic,  homogeneous,  solid, 
liquid,  or  gas.  When  solid,  it  is  usually  crystallized. 

Artificial  substances  such  as  are  produced  in  laboratories,  chemical 
works,  iron  foundries,  etc.,  are  excluded  from  the  definition,  although 
they  often  show  perfection  of  form  and  purity  of  constitution.  Min- 
eralogy is  concerned  with  natural  products. 


GUIDE  TO  MINERAL  COLLECTIONS 


The  term  inorganic  excludes  all  forms  of  living  substance — every- 
thing that  grows  by  internal  activity,  that  has  the  power  of  assimila- 
tion and  reproduction,  that  has  sensibility  and  usually  slight  chemical 
stability.  A  mineral  may  have  had  an  organic  origin.  For  example, 
the  carbon  of  a  piece  of  graphite  may  have  been  at  one  time  in  a  tree. 
The  tree  died  and  with  the  loss  of  oxygen  and  hydrogen  was  converted 
into  peat.  The  loss  of  oxygen  and  hydrogen  continuing,  the  peat  or 
lignite  was  changed  into  bituminous  coal,  then  into  anthracite,  and 
finally  into  graphite.  It  is  not  the  origin  but  its  present  condition 
which  places  a  substance  in  the  mineral  kingdom. 

The  term  homogeneous  indicates  that  the  substance  throughout 
is  the  same  at  one  point  as  another,  has  the  same  arrangement,  and 
shows  the  same  properties.  This  separates  a  mineral  from  other 
inorganic  substances  such  as  rocks.  A  rock  is  made  up  of  a  mass  of 
minerals. 

Usually  a  mineral  is  a  solid.  Some  minerals — for  example,  water 
and  mercury — are  ordinarily  liquid  but  may  be  changed  into  solids 
by  freezing:  water  at  32°  and  mercury  at  —40°  F.  All  minerals  are 
solid  under  certain  conditions. 

Minerals  are  usually  crystallized;  that  is,  they  have  a  definite 
internal  structure  which  is  often  shown  by  their  external  form.  There 
are  a  few  exceptions,  such  as  turquoise  and  opal,  and  other  substances 
which  are  solidified  from  gases  or  liquids  so  rapidly  or  under  such 
other  unfavorable  conditions  that  the  molecules  are  unable  to  properly 
arrange  themselves.  These  minerals  are  said  to  be  amorphous. 
They  may  be  regarded  as  minerals  that  are  unsuccessful  or  are  of 
weak  molecular  attractions.  Ordinarily  a  mineral  has  just  as  definite 
a  shape  as  has  a  bird  or  a  flower.  It  has  less  opportunity  than  a 
flower  to  develop  a  perfect  external  form,  since  it  is  usually  crowded 
by  its  neighbors.  The  growing  crystal  soon  reaches  a  place  where 
its  planes  touch  those  of  its  neighbors  and  its  perfection  is  impaired. 
But  though  the  bounding  planes  are  distorted  and  irregular,  the 
internal  arrangement  is  so  orderly  and  definite  that  the  smallest 
fragment  has  the  same  structure  as  a  perfect  crystal. 

This  regularity  of  architecture  in  the  mineral  world  is  a  fact  of 
far-reaching  importance.  It  discloses  one  of  the  great  laws  of  the 
universe,  a  law  as  beautiful  and  universal  as  the  law  of  gravitation, 
the  conservation  of  energy,  or  the  development  of  species. 


INTRODUCTION  3 

The  law  of  crystallization  affects  every  particle  of  mineral  matter 
in  the  world,  and  more  than  that,  in  the  universe  as  well.  The  results 
are  seen  alike  in  the  minutest'  forms  and  on  a  gigantic  scale.  The 
most  beautiful  colors  in  the  world — the  pure  colors  of  the  spectrum — 
are  exhibited  by  minerals  in  accordance  with  this  law. 

Minerals  are  the  most  abundant  and  most  valuable  substances 
in  the  world. 

If  all  the  vegetation  in  the  world — the  great  masses  of  weeds  in 
Sargasso  Seas,  the  myriads  of  land  weeds,  the  flowers  and  grains, 
all  the  trees  of  the  mighty  forests — if  all  of  these  were  placed  in  an 
immense  pile  and  to  this  pile  were  added  all  the  lower  animals,  all 
mankind,  and  all  the  buildings  in  the  world,  the  mass  would  be 
gigantic.  But,  if  in  another  pile  were  heaped  the  minerals  of  which 
the  world  is  composed,  the  first  pile  would  be  as  a  grain  of  sand  to  a 
mountain,  so  small  as  to  be  well-nigh  invisible.  In  quantity  minerals 
are  of  the  greatest  importance. 

In  quality  the  same  is  true.  They  are  unsurpassed  in  enduring 
beauty  and  value.  Some  diamonds  like  the  Kohinoor,  Regent,  or 
the  Cullinan  are  valued  more  highly  than  any  other  objects  of  the 
same  size  in  the  world.  A  ruby  worth  half  a  million  dollars  is  so 
light  in  weight  that  it  could  be  sent  by  mail  across  the  continent  for 
two  cents.  Mineral  ornaments  such  as  vases,  tables,  and  columns 
in  the  palaces  of  the  wealthy  and  in  the  great  museums  will  remain 
unchanged  in  beauty  and  pleasure-giving  power  for  many  long 
years.  Minerals  are  as  beautiful  as  flowers  and  infinitely  more 
permanent. 

Though  the  same  sun  with  all  diffusive  rays 
Blush  in  the  rose  and  in  the  diamond  blaze, 
We  prize  the  higher  effort  of  his  power 
And  justly  place  the  gem  above  the  flower.1 

An  acquaintance  with  minerals  is  useful  in  many  trades  and  pro- 
fessions. The  doctor  of  medicine  and  the  pharmacist  may  be  inter- 
ested in  minerals  as  the  source  of  drugs.  The  lawyer  may  be  helped 
by  some  knowledge  of  mineralogy,  especially  in  mining  cases.  The 
minister  furnished  by  this  science  with  an  insight  into  the  structure 
of  the  universe  is  better  able  to  find  "sermons  in  stones."  From 

1  Alexander  Pope. 


4  GUIDE  TO  MINERAL  COLLECTIONS 

the  study  of  the  mineral  composition  of  his  soil  the  farmer  is  aided  in 
soil  improvement  and  in  making  " bread  from  stones."  The  physicist 
repeatedly  uses  minerals  in  his  study  of  the  laws  of  heat,  light,  and 
electricity.  Even  more  dependent  upon  minerals  as  a  source  of 
materials  for  study  and  experiment  is  the  chemist.  For  the  geologist? 
the  prospector,  the  miner,  the  assayer,  and  the  metallurgist,  min- 
eralogy is  a  fundamental  science,  one  without  which  they  cannot 
well  work. 

Thus  the  mineral  collections  in  the  museum  have  a  twofold  claim 
upon  the  interest  of  the  visitor:  first,  because  they  well  illustrate  the 
mineral  resources  of  this  state,  and  second,  because  they  show  the 
composition  of  the  world  and  the  uses  which  our  people  make  of 
minerals  to  increase  the  comfort  of  living  and  their  happiness. 

The  visitor  will  naturally  begin  his  inspection  of  this  collection 
with  the  minerals  that  are  the  most  simple  in  their  composition — 
those  that  are  composed  of  but  one  chemical  substance,  the  so-called 
elements.  He  will  find  that  while  there  are  about  two  dozen  of  them 
which  occur  in  some  abundance  as  minerals,  not  more  than  twelve 
are  common  enough  to  claim  his  attention.  These  are:  diamond, 
graphite,  sulphur,  arsenic,  antimony,  bismuth,  gold,  silver,  copper, 
mercury,  platinum,  and  iron.  Each  of  these  is  noteworthy  because  of 
its  beauty  or  utility  or  because  it  shows  some  peculiar  property.  All 
of  them  except  antimony,  bismuth,  mercury,  and  platinum  have 
been  found  in  the  state.  Diamond,  graphite,  and  sulphur  are  non- 
metals;  antimony  and  bismuth,  brittle  metals;  gold,  silver,  copper, 
platinum,  and  iron,  malleable  metals;  and  mercury,  a  liquid  metal 
under  ordinary  conditions.  Together,  these  minerals  constitute  the 
most  prominent  representatives  of  Class  I. 


PLATE  I 


* 


a,  Prevailing  forms  of  the  diamond.     G.  F.  Williams  collection 


b,  Glass  model  of  Cullinan  diamond,  the  largest  diamond  ever  found 


CLASS  I.    ELEMENTS 


Diamond 

There  are  several  reasons  for  studying  the  diamond  first,  though 
Illinois  is  not  a  diamond-producing  state.  Not  more  than  a  dozen 
diamonds  have  been  found  here  and  they  are  immigrants  brought  in 
by  glaciers  which  formerly  slid  down  from  the  north,  carrying  all 
kinds  of  minerals  collected  from  a  wide  area  and  scattering  them 
here  and  there  over  two- thirds  of  the  state.  The  chief  source  of 
the  diamond  is  the  Kimberley  region  in  South  Africa,  but  no  people 
are  more  partial  to  the  diamond  as  a  gem  than  are  the  citizens  of 
this  state.  Every  woman  has  or  expects  to  have  one,  and  every  man 
should  at  some  time  buy  one ! 

The  diamond  is  easily  premier  among  gems.     It  is  a  fine  example 
of  a  successful  mineral.     Its  character  is  positive.     It  deserves  the 
most    extended    study.      While 
studying  it  we  gain  an  insight 
into    the   whole   mineral  world. 
The  Illinois  State  Museum  con- 
tains   a    few    examples    of    the 
diamond,   and    glass    models   of 
the   most   famous   diamonds   of 
history.     If  one  examines  a  hand- 
ful of  diamonds  as  they  are  taken 
from    the   mines   at    Kimberley 
(Plate  I)  or  as  they  come  uncut 
to  Amsterdam,  London,  or  New 
York  City,  he  will  observe  that 
the  greater  number  of  them  are 
shaped  like  two  pyramids  placed 
base  to  base  forming  an  eight- 
sided  figure  called  an  octahedron  (Fig.  i).     Some  of  them  are  flat, 
triangular  flakes,  others  globules,  and  nearly  all  are  somewhat  dis- 
torted and  pitted,  with  some  planes  well  developed  and  others  small. 
The  larger  faces  were  formed  on  that  side  of  the  crystal  which  had 


FIG.  i.— Model  of  octahedron; 
vailing  outline  of  diamond. 


pre- 


6  GUIDE  TO  MINERAL  COLLECTIONS 

the  most  abundant  material  to  draw  from,  while  the  small  faces, 
like  the  smaller  birds  in  a  nest,  receiving  the  least  food,  have  not 
had  equal  opportunity  for  growth.  But  while  the  different  faces 
vary  in  size,  the  angles  between  them  are  always  the  same.  They 
are  said  to  be  constant,  and  illustrate  the  "law  of  constancy  of 
angle  " — a  law  of  far-reaching  importance,  since  because  of  it  minerals 
can  readily  be  identified  and  classified. 

The  natural  shape  of  a  mineral  is  one  of  the  first  characters  to 
notice.  What  anatomy  is  to  the  student  of  the  human  body,  cell 
structure  to  the  morphologist,  and  architecture  to  the  builder,  crystal 
form  is  to  the  mineralogist.  It  is  one  of  the  fundamentals.  The 
purpose  of  study  of  the  form  of  minerals  is  not  only  to  recognize  and 

picture  the  external  form  but  to 
understand  the  internal  structure 
as  well,  since  they  are  dependent 
upon  each  other. 

The   architecture   of   the  dia- 
mond may  be  better  understood  if 

JL+          the  planes  which  occur  on  natural 

crystals  can  be  represented  by  a 
drawing.  Fortunately  it  is  only 
necessary  to  measure  off  certain 
points  and  connect  them  by  straight 
lines — a  much  simpler  task  than  it 
FIG.  2.— Axes  would  be  to  draw  the  structures 

seen    in    the    plant    and    animal 
worlds.    Anyone  can  draw  the  shapes  which  diamonds  exhibit. 

First  draw  three  lines  or  axes  which  intersect  each  other  at  right 
angles  (Fig.  2).  In  drawing  these  figures  we  use  the  method  most 
generally  employed,  which  is  called  "  clinographic  projection."  The 
eye  is  supposed  to  be  elevated  a  trifle  above  the  crystal  and  removed 
an  infinite  distance  so  that  the  lines  in  the  drawing  do  not  converge 
as  in  ordinary  perspective.  Those  parallel  in  the  crystal  are  parallel 
in  the  drawing. 

To  erect  the  axes,  a  templet  cut  out  of  cardboard  may  be  con- 
structed in  the  following  manner  (Fig.  3) : 

Draw  a  vertical  line  MM'  and  NN'  at  right  angles  to  it.  Divide 
NN'  into  six  equal  divisions.  At  the  second  and  fourth  divisions 


_.**. 


ELEMENTS 


draw  lines  parallel  to  MM'.  From  Nf  mark  N'O  equal  to  one  divi- 
sion. From  0  draw  a  straight  line  through  P  to^O'.  ad  is  the  front 
to  back  axis  of  our  crystal.  From  a  draw  aR  parallel  to  N'N.  From 
R  draw  RP.  From  S  draw  Sb  parallel  to  NN'.  From  b  draw  bP  and 
extend  to  b.  bb  is  the  horizontal  axis  extending  from  right  to  left. 
Twice  OP  gives  the  length  of  the  c  axis.  These  axes  form  the  founda- 
tion for  the  construction  of  the  axes  used  all  through  the  work.  An 
excellent  discussion  of  the  subject  may  be  found  in  Tutton's  Crystal- 
lography.1 We  always  call  the  vertical  line  (Fig.  2)  c;  the  horizontal 


M 


N1 


R 
O 


c 
M' 


FIG.  3. — Method  of  constructing 
crystallographic  axes. 


FIG.  4. — Construction  of  an  octa- 
hedral plane. 


line,  extending  from  right  to  left,  b;  and  the  one  extending  from  the 
front  backward,  a.  The  upper  half  of  the  c  axis,  the  right  half  of  b, 
and  the  front  of  a  are  said  to  be  positive;  the  others,  negative.  To 
draw  any  given  plane  mark  the  points  at  which  it  would  intersect 
the  axes.  In  the  octahedron  (Fig.  i)  each  plane  intersects  the  three 
axes  at  points  equally  distant  from  the  center.  Then  to  draw  an 
octahedral  plane  measure  off  equal  distances  on  each  axis  and  connect 
these  points  with  straight  lines  (Fig.  4).  To  complete  the  octahedron, 
which  has  eight  such  planes,  draw  similar  planes  in  each  of  the  other 
octants  (Fig.  5). 

'Seepages  382-439. 


8 


GUIDE  TO  MINERAL  COLLECTIONS 


The  relation  of  the  axes  to  each  other  was  expressed  by  an  Eng- 
lish mineralogist,  W.  H.  Miller,  of  Cambridge  (d.  1880),  as  a  ratio, 
a:  b :  c.  The  portion  measured  off  on  each  axis  is  written  as  a  denomi- 
nator. Then  the  ratio  which  represents  the  octahedral  plane  is 

-:-:-,  and  its  symbol  is  (in)  which  is  read  as  one,  one,  one.     When 

simply  (in)  is  used,  the  right-hand  upper  octant  is  meant.     The 

left-hand  upper  octant  would 

c  have  the  symbol  (111)  [read 

one,  minus  one,  one];  the 
right-hand  lower  (111), 
the  left-hand  lower  (in),  the 
right-hand  upper  back  (in), 
the  left-hand  upper  back 
(in),  etc. 

The  diamond,  like  some 
other  minerals,  is  symmetri- 
cally built.  It  has  the  same 
molecular  structure  in  all 
directions.  Light,  heat,  and 
electricity  travel  through  it 
with  the  same  ease  and 
rapidity  in  the  direction  of 
all  three  of  the  axes,  and 
the  corrosive  action  of  sol- 
vents is  the  same  in  all  parts.  Its  axes  are  of  the  same  value  and 
interchangeable,  and  hence  a  numeral  like  i  may  be  substituted  for 

the  letters  a,  b,  and  c  and  the  ratio  - :  - :  -  then  becomes  -:-:-.     This 

iii  iii 

cleared  of  fractions  yields  i :  i :  i.  The  numbers  in  this  ratio,  i :  i :  i, 
constitute  the  " parameters"  of  the  octahedral  plane,  since  they 
define  the  position  of  the  plane.  The  parameter  of  another  plane 
might  be  1:2:2  or  2:1:2,  etc. 

The  plane  which  has  the  parameter  1:2:2  represents  a  ratio  - :  - : 

and  its  symbol  is  (211)  (Fig.  6).  Since  each  of  the  three  axes  are 
equal,  we  can  apply  the  2  to  each  axis  in  turn  and  hence  obtain 
three  planes  in  every  octant. 


FIG.  5. — Completed  octahedron 


—  6- 


Construction  of  right-hand  upper  octant  of  a  trisoctahedron  above,  and  of  a 
trapezohedron  below. 


ELEMENTS 


Parameters 


2:i:2 


2:2:i 


Ratios 
I.I.I 
2*1*1 
III 
I*2'l 

I.I.I 
1*1*2 


Symbols 
(211) 

(121) 
(112) 


To  construct  these  three  planes  in  the  right-hand  upper  octant 
(Plate  II,  lower  diagram)  measure  off  unit's  distance  on  a  and  draw  a 
line  (red)  cutting  b  at  twice  unit's  distance,  one  cutting  c  at  twice  unit's 
distance,  and  one  connecting  the  ends  of  b  and  c.  Then  from  unit's 


FIG.  6. — Model  of  trapezohedron 


FIG.  7. — Completed  trapezohedron 


distance  on  b  draw  lines  (blue)  cutting  a  and  c  at  twice  unit's  dis- 
tance, and  connect  the  ends.  Finally,  beginning  at  unit's  distance 
on  c  draw  lines  (green)  cutting  a  and  b  at  twice  unit's  distance  and 
connect  the  ends.  These  lines  will  determine  the  position  of  planes 
which  will  intersect  each  other  so  as  to  form  three  trapezoids  in 
the  octant.  When  the  same  plan  is  followed  for  the  other  octants 
there  results  a  trapezohedron  (Figs.  6  and  7). 

Having  constructed  figures  with  the  symbol  (in)  and  (211),  the 
next  in  order  will  be  one  with  the  symbol  (221)  (Fig.  8).     Its  ratio 

will  be  -:-:-  and  its  parameter  1:1:2.    Just  as  in  the  case  of  the 


221 


10 


GUIDE  TO  MINERAL  COLLECTIONS 


trapezohedron,  the  numerals  may  be  applied  to  each  of  the  axes  in 
turn.  Thus  writing  the  parameters,  ratios,  and  symbols  for  the 
right-hand  upper  octant  w.e  obtain  the  following: 


Parameters 


Ratios 
III 


III 


III 


Symbols 
(221) 

(122) 
(212) 


Draw  a  line  (red)  cutting  a  and  b  at  unit's  distance  and  c  at  twice 
unit's  distance   (Plate  II,  upper  diagram).     From  unit's  distance 


FIG.  8— Model  of  trisoctahedron 


FIG.  9. — Trisoctahedron  completed 


on  b  draw  lines  (blue)  cutting  a  at  twice  unit's  distance  and  c  at 
unit's  distance.  From  unit's  distance  on  c  draw  lines  (green)  cutting 
a  at  unit's  and  b  at  twice  unit's  distance.  These  lines  determine  the 
position  of  planes  which  intersect  within  the  octant  so  as  to  produce 
triangles.  The  resulting  planes  are  called  trisoctahedral  planes  and 
the  figure  produced  by  continuing  the  process  in  each  octant  is  called 
the  trisoctahedron  (Figs.  8  and  9). 


PLATE  III 


Construction  of  one  octant  of  hexoctahedron 


ELEMENTS  II 

The  next  form  in  point  of  complexity  is  one  whose  planes  intersect 
each  axis  at  different  distances  (Fig.  10).     For  example,  its  parameter 

might  be  i  :  -  :  3  ;  its  ratio  then  would  be  -:-:-,  and  its  symbol  (321). 

Since  each  number  in  the  parameter  is  different,  each  of  the  three 
axes  would  be  intersected  at  two  points  different  from  unity  and  there 
would  result  two  planes  at  each  corner  of  the  octant,  making  six  planes 
where  the  octahedron  has  but  one. 

Writing  the  parameters,  ratios,  and  symbols  as  before,  the  follow- 
ing result: 

Parameters  Ratios  Symbols 

3  III  ,         N 

i:-:3  -----  (321) 

a  3  2  i 

;|        3:i:3       I     v:i  (23I) 


3=1=1 


Proceed  in  the  construction  as  was  done  with  the  octahedron, 
trapezohedron,  and  trisoctahedron.  To  construct,  begin  at  unit's 
distance  on  a  (Plate  III)  and  draw  a  line  (red)  cutting  b  at  three  halves 
unit's  distance  and  one  cutting  c  at  three  times  unit's  distance.  Com- 
plete the  triangle  by  joining  f&  and  3^.  Begin  at  unit's  distance 
on  b  and  draw  a  line  (blue)  cutting  a  at  three  halves  unit's  distance 
and  one  cutting  c  at  three  times  unit's  distance.  Join  f#  and  $c. 
Again  from  unit's  distance  on  b  draw  other  lines  (blue  dotted)  cutting 
a  at  three  times  unit's  distance  and  c  at  three  halves.  Join  the  ends. 
Continue  the  construction  from  c  (with  green)  and  a  (with  red  dotted) 
as  indicated  and  the  six  planes  of  the  octant  will  be  produced.  They 
are  called  the  hexoctahedral  planes.  The  same  operation  repeated 
in  each  octant  produces  a  hexoctahedron  (Figs.  10  and  n). 


12 


GUIDE  TO  MINERAL  COLLECTIONS 


The  faces  above  described  are  those  most  characteristic  of  the 
diamond,  but  usually  faces  of  any  one  form  do  not  make  up  the 
whole  crystal.  Sometimes  planes  of  one  form  predominate  and  small 


FIG.  10. — Model  of  hexoctahedron 


FIG.  ii. — Hexoctahedron  completed 


FIG.  12. — Growth  of  unshaded 
planes  of  the  wooden  octahedron 
produce  the  glass  tetrahedron 
covering  it. 


FIG.  13. — Right-handed  tetrahedron 


faces  of  another  modify  the  corners.  Often  two  crystals  will  inter- 
penetrate, each  crystal  having  only  half  of  its  faces  developed.  If 
the  right-hand  upper  octant  and  every  alternate  octant  of  the  octa- 
hedron should  grow  to  the  exclusion  of  the  other  faces,  a  tetrahedron 


ELEMENTS 


(Figs.  12  and  13)  would  result.  If  the  left-hand  upper  octant  and 
each  alternate  octant  were  developed,  a  left-handed  or  negative 
tetrahedron  would  be  produced  (Figs.  14  and  15). 


FIG.  15. — Left-handed  tetrahedron 


FIG.  14. — Wooden  octa- 
hedron inclosed  by  glass 
tetrahedron. 

When  two  supple- 
mentary tetrahedrons 
interpenetrate,  the  form 
represented  in  Figure  16 
results.  It  is  called  an 
interpenetrating  tetrahe- 
dral  twin.  Where  an  octa- 
hedron would  have  sharp 
edges,  these  tetrahedral 
twins  have  re-entrant 
angles. 

Now  if  the  projecting 
corners  of  each  tetrahe- 
dron were  truncated  by 
the  faces  of  the  other  tetrar 
hedron,  a  form  resembling 

an  octahedron  would  result,  but  trie  re-entrant  angles,  instead  of  the 
characteristic  edges,  would  reveal  its  true  structure.  This  is  a  very 
common  occurrence  in  the  diamond  (Fig.  17). 


FIG.    1 6. — Interpenetrating  supplementary 
tetrahedrons  (tetrahedral  twins). 


14  GUIDE  TO  MINERAL  COLLECTIONS 

Just  as  with  the  octahedron,  so  also  with  the  trapezohedron, 
trisoctahedron,  or  the  hexoctahedron,  a  portion  only  of  the  faces 
might  be  developed.  If  the  right-hand  upper  octant  and  every 
alternate  octant  of  a  hexoctahedron  were  produced  at  the  expense 
of  their  neighbors,  a  right-handed  hexatetrahedron  would  result 
(Figs.  1 8  and  19). 


FIG.  17. — Tetrahedral  twin  with  corners  truncated 

A  left-handed  or  negative  hexatetrahedron  would  be  produced 
if  the  left-hand  upper  and  every  alternate  octant  were  developed  at 
the  expense  of  their  neighbors.  A  right-handed  and  a  left-handed 
hexatetrahedron  interpenetrating  and  having  the  corners  truncated 
by  tetrahedral  planes  give  rise  to  one  of  the  most  characteristic  forms 
of  the  diamond  (Fig.  20). 

Upon  taking  up  a  diamond,  one  first  notices  the  prevailing 
octahedral  form,  but  closer  inspection  reveals  the  re-entering  angles, 
and  in  these  angles  the  slightly  inclined  hexatetrahedral  planes  may 
be  recognized. 


ELEMENTS  15 

Another  form  of  twinning  in  the  diamond  is  that  which  results 
when  an  octahedron  is  cut  through  the  middle  by  a  plane  parallel 
to  an  octahedral  face  and  one-half  of  the  octahedron  is  turned  90° 
(as  shown  in  Figs.  21  and  22).  Diamonds  of  this  sort  are  called 
" suture"  stones  by  diamond  dealers  and  by  crystallographers  "spinel 
twins/'  since  they  are  even  more  commonly  found  among  specimens 
of  the  mineral  named  spinel. 

All  of  the  above  forms — the  octahedron,  the  trapezohedron, 
trisoctahedron,  hexoctahedron,  tetrahedron,  and  hexatetrahedron — 
agree  in  this,  that  they  are  symmetrical  in  the  same  directions.  If 


FIG.    1 8.— Model   of   right-handed 
hexatetrahedron . 


FIG.    19. — Construction   of   hexatet- 
rahedron. 


any  of  these  forms  were  divided  parallel  to  these  directions,  one-half 
would  be  just  like  the  other. 

These  directions  are:  first,  parallel  to  any  one  of  the  three  crystal- 
lographic  axes,  a,  b,  and  c  (Fig.  23);  second,  parallel  to  any  one  of  the 
four  axes  perpendicular  to  the  octahedral  planes;  third  (Fig.  24), 
parallel  to  the  six  planes  which  would  pass  through  the  edges  of  a 
cube.  Since  this  symmetry  is  best  represented  in  a  mineral  called 
tetrahedrite,  it  is  named  the  tetrahedrite  class  of  symmetry. 

By  the  above  study  we  have  become  acquainted  with  facts  in 
regard  to  the  crystallography  of  the  diamond  and,  more  than  that, 
with  facts  which  are  needed  to  understand  the  forms  of  a  hundred 


16  GUIDE  TO  MINERAL  COLLECTIONS 

other  minerals  as  well.  All  of  these  minerals  agree  in  this,  namely, 
that  the  molecules  which  compose  them  arrange  themselves  similarly 
along  three  lines  of  equal  length  at  right  angles  to  each  other,  the  a,  b, 
and  c  axes.  Hence  these  minerals  are  placed  together  in  one  of  the 
six  great  groups  in  which  all  minerals  are  classified — the  group  known 
as  the  Regular  System. 


FIG.  20. — Interpenetrating  truncated  tetrahedrons  beveled  by  hexatetrahedrons 

As  wood  has  certain  directions  in  which  it  readily  splits  and  con- 
trary to  which  it  breaks  in  an  irregular  manner,  so  the  diamond  has 
a  direction  in  which  it  readily  splits  or  "  cleaves,"  namely,  parallel 
to  the  octahedral  planes.  By  taking  advantage  of  the  cleavage, 
diamond  cutters  are  more  readily  able  to  fashion  the  gem  into  the 
desired  shape.  Cleavage  is  so  easily  obtained  that  it  is  difficult  to 
break  or  "  fracture  "  the  diamond.  When  it  is  broken  and  not  cleaved 
or  split,  the  fractured  surfaces  are  pitted  or  rounded  like  a  shell. 
Consequently  the  fracture  is  said  to  be  conchoidal. 

Contrary  to  popular  report,  the  diamond  is  brittle  and  easily 
shattered.  Many  valuable  gems  have  been  destroyed  by  the  finders, 


ELEMENTS 


who  failed  to  recognize  the  difference  between  hardness  and  tenacity. 
For  centuries  it  has  been  a  tradition  that  if  a  diamond  were  laid  upon 
an  anvil  and  struck  by  a  hammer,  both  anvil  and  hammer  would  fly 
to  pieces  before  the  diamond  was  broken.  Pliny  said  that  the  only 
way  to  "subdue"  a  diamond  is  to  "soften  it  in  warm  goat's  blood"! 
Although  the  diamond  is  brittle,  it  is  the  hardest  of  minerals. 


FIG.  2i.— "Spinel  twin"  model.    Twin- 
ning plane  (in). 


FIG.  22. — Drawing  of  spinel  twin 


Scale  of  Hardness 


To  measure  the  hardness  of  minerals  a  scale 


1.  Talc 

2.  Gypsum 

3.  Calcite 

4.  Fluorite 

5.  Apatite 

6.  Orthoclase 

7.  Quartz 

8.  Topaz 

9.  Corundum 
10.  Diamond 


has  been  arranged  which  consists  of  ten  minerals 
so  chosen  that,  beginning  with  the  softest,  each 
succeeding  mineral  is  hard  enough  to  scratch  the 
one  before  it  in  the  scale.  Talc,  which  is  the 
softest,  is  given  as  No.  i  in  this  list,  and  diamond 
as  No.  10.  The  finger-nail  can  scratch  any  mineral 
below  3,  and  a  knife-blade  any  below  6. 
When  the  weight  of  the  diamond  is  compared  with  that  of  an 
equal  volume  of  water,  the  diamond  is  found  to  be  three  and  one- 
half  times  as  heavy  as  water,  i.e.,  its  specific  gravity 
is  3  .5.  It  is  much  heavier  than  glass  (sp.  gr.  about 
2.5),  which  is  most  commonly  employed  to  imitate 
it,  or  quartz  (sp.  gr.  2.6),  the  most  abundant 
mineral  that  resembles  diamond,  or  phenacite,  "  the 


Specific  Gravity  of 

1.  Glass  2.5 

2.  Quartz  2.6 

3.  Phenacite  2.9 

4.  Topaz  3 . 5 


i8 


GUIDE  TO  MINERAL  COLLECTIONS 


deceiver"  (sp.  gr.=3),  which  is  sometimes  worn  to  represent  the 
more  valuable  gem. 

The  diamond  shows  color  from  two  causes:  first,  because  of  actual 
coloring  materials  in  it;  and  second,  because  it  divides  a  ray  of  enter- 
ing light  into  the  colors  of  the  spectrum.     The  coloring  matter  is 
usually  some  metallic  oxide  which  does  not  change  when  heated. 
Sometimes  the  coloring  matter  is  organic  material  which  does  fade 
when  heated  or  held  in  sunlight.     Many  shades  are  seen — red,  yel- 
low, green,  blue,  indigo, 
brown.     Yellow    and 
brown  are  the  most  com- 
mon among  African  dia- 
monds.    Brown   may 
deepen  into  black,  as  in 
the   opaque    ''carbons." 
Green  is  not  so  common. 
Blue   and   red    are    the 
rarest,  and   when   these 
colors  are  pure,  the  dia- 
mond exhibiting  them  is 
the  most  valuable   gem 
in  the  world.    About  half 
of   all    diamonds   found 
are   white    or    colorless. 
The     color     or     "fire" 
which  they  then  show  is 
due  to  the  fact   that  a 

ray  of  light  which  enters  at  an  angle  is  refracted  or  turned  very 
markedly  from  its  course  and  is  divided  into  rays  of  different  wave- 
lengths. The  result  obtained  by  dividing  the  angle  which  the  entering 
light  makes  with  a  perpendicular  erected  to  the  surface  of  the  mineral 
(called  the  angle  of  incidence,  i  in  Fig.  25)  by  the  angle  which  the  ray 
makes  with  the  perpendicular  prolonged  after  it  has  entered  the 
mineral  (called  the  angle  of  refraction,  r  in  the  figure)  is  called  the 
index  of  refraction.  Thus 


FIG.  23. — Two  kinds  of  axes  of  symmetry 


n  = 


Sin  I 
sin  r 


ELEMENTS  19 

The  index  of  refraction  n  has  a  different  value  according  to  the 
kind  of  light  used.  For  blue  light  in  the  diamond  it  is  2.465;  for 
red,  2.402.  That  is,  a  blue  ray  is  turned  farther 
from  a  straight  line  than  is  a  red  ray.  Now  the 
difference  between  these  indexes,  0.063,  *s  called 
the  dispersion.  Both  the  refraction  and  disper- 
sion of  diamonds  are  high  in  comparison  to  the 
refraction  and  dispersion  of  other  minerals.  Because 
of  its  high  refraction  the  diamond  is  unusually 
brilliant.  It  is  said  to  show  "life."  Because  of 
its  high  dispersion  it  has  a  remarkably  vivid  play  of 
colors  or  "fire." 


Mean  Refractive 
Index  of 

Ice  1.31 
Salt  i .  54 
.Quartz  1.55 
Topaz  1.62 
Glass  i .  80 
Cinnabar  3  .02 


Dispersion  of 

Fluorite  .006 
Quartz  .025 
Diamond  .063 


^•^TI 

~--^\ 

\                       / 

r^        i 

\                    / 

\           / 

\                 / 

\        I 

\                s 

X 

\     / 

\            • 

\  / 

*X 

/\ 

^  \ 

/       \ 

/     \ 

/ 

/      \ 
/         \ 

./,.-  \- 

1           \ 

/£•**'                      v 

L^^ 

FIG.   24. — Dotted  lines  show  direction         FIG.  25. — Angles  of  incidence  and 
of  planes  of  symmetry  in  cube.  refraction. 


Some  diamonds  which  have  a  bluish  tinge  after  being  held  in 
the  sunlight  emit  light  in  the  dark,  i.e.,  become  phosphorescent. 
Many  phosphoresce  after  being  rubbed  on  wood  or  while  being 
subjected  to  an  electric  discharge  in  a  vacuum  or  while  exposed  to 
radium  emanations.  Positive  electricity  is  developed  in  the  diamond 
by  friction. 

The  diamond  is  worthy  of  its  place  as  the  leading  gem,  not  only 
because  of  its  hardness,  brilliancy,  and  beauty  of  color,  but  also 
because  of  its  permanency  in  the  presence  of  corrosive  gases  and 
liquids.  The  air  and  moisture  do  not  affect  it.  Ordinary  acids 


20  GUIDE  TO  MINERAL  COLLECTIONS 

cannot  dissolve  it.  A  solvent  composed  of  sulphuric  acid  and  potas- 
sium bichromate  acts  upon  it  slowly.  At  a  high  temperature  (goo0C. ) 
in  an  oxygen  flame,  the  diamond  burns  to  carbon  dioxide  just  as 
pure  charcoal  does,  and  sometimes  leaves  an  extremely  light  ash  that 
retains  the  original  crystal  shape  and  consists  of  iron,  calcium, 
magnesium,  and  silicon  which  were  present  as  impurities. 

Though  used  as  a  gem  for  many  hundreds  of  years,  it  is  only  within 
comparatively  recent  times  that  cutting  of  the  diamond  has  been 
resorted  to  to  enhance  its  beauty.  Cutting  and  polishing  are  accom- 
plished by  the  use  of  diamond  dust  imbedded  in  a  tin  disc  or  an  iron 
plate. 

Besides  its  use  as  a  cutting  tool,  in  its  less  well-crystallized  forms 
it  is  extensively  used  to  make  drills.  The  diamond  drill  is  one  of  the 
most  useful  implements  invented  for  piercing  rock  in  the  search  for 
valuable  ores.  The  drills  are  made  from  the  forms  of  diamond  called 
bort  and  carbonado.  Bort  has  radial  fibrous  structure,  curved  drusy 
surface,  and  is  dark  in  color.  Carbonado  is  somewhat  compact, 
altogether  without  cleavage,  slightly  porous,  black  like  charcoal,  and 
somewhat  harder  than  ordinary  diamond.  It  is  valuable  for  drills. 

Diamonds  have  been  found  in  nearly  every  part  of  the  globe,  yet 
for  some  cause  or  other  in  quantities  worth  mentioning  only  in  regions 
less  than  30°  from  the  equator.'  A  line  following  their  most  abundant 
occurrence  would  begin  in  southeastern  Australia  and  extend  east- 
ward to  South  America;  there,  dividing  into  two  branches,  would 
pass  in  one  branch  north  of  the  equator  to  British  Guiana,  and  in  the 
other,  south  to  Bahia  in  Brazil.  The  northern  branch  extended  would 
finally  reach  India,  most  prolific  of  ancient  localities,  and  the  southern 
branch  would  reach  South  Africa  at  Kimberley,  the  most  productive 
of  modern  regions. 

In  India  diamonds  were  first  found  and  prized  as  gems.  Most 
of  the  famous  historical  gems  came  from  there.  That  field  is  now 
exhausted.  The  New  South  Wales  fields  yield  about  sixty  thousand 
dollars'  worth  a  year,  British  Guiana  twice  that  amount,  and  Brazil 
five  times  that  amount,  while  South  Africa  so  far  surpasses  these 
regions  as  to  make  them  hardly  worth  mentioning.  It  easily  produces 
twenty-five  million  dollars'  worth  annually. 

In  India,  Australia,  South  America,  and  also  in  a  few  localities 
in  the  Urals,  and  in  Wisconsin,  Michigan,  Illinois,  etc.,  diamonds 


ELEMENTS  21 

have  been  found  in  sands  and  gravels  in  which  they  were  imbedded 
when  the  original  rock  containing  them  was  broken  up  and  trans- 
ported by  glaciers  or  flowing  streams. 

In  the  Kimberley  region,  however,  they  occur  in  a  greenish-blue 
igneous  rock  called  kimberlite,  a  sample  of  which  is  shown  in  Case  i . 

The  kimberlite  occupies  crater-like  basins,  sometimes  nearly  half 
a  mile  in  diameter  and  of  unknown  depth,  in  the  Triassic  rocks  of 
that  region. 

In  Arkansas  kimberlite  has  been  found  and  has  yielded  a  few 
diamonds. 

Meteorites  often  contain  minute  diamonds. 

Glass  models  of  diamonds  of  unusual  size  and  value,  several  of 
which  have  been  long  known  and  owned  by  kings  and  other  celeb- 
rities, are  shown  in  Case  i.  No  diamond  is  more  famous  than 
the  Kohinoor.  It  weighs  106  carats  and  is  valued  at  more  than 
half  a  million  dollars.  It  was  found  in  India  six  hundred  years  ago 
(1304  A.D.)  and  for  centuries  was  fought  for  or  purchased  by  various 
rulers.  It  is  now  exhibited  among  the  English  crown  jewels  in 
London. 

The  Regent,  which  weighs  136  carats  and  is  valued  at  six  hundred 
thousand  dollars,  has  had  a  most  eventful  history  from  the  time 
when  it  was  found  in  India  by  a  slave,  stolen  from  him  by  a  sailor, 
bought  and  sold  at  ever-increasing  price,  till  it  came  to  sparkle  in 
the  hilt  of  Napoleon's  sword,  and  finally,  as  one  of  the  gems  of  the 
French  Republic,  was  placed  where  it  could  ever  after  be  inspected 
by  all  who  cared  to  see  it  in  the  priceless  collections  of  the  Louvre, 
Paris. 

The  next  is  the  Orloff,  193  carats,  valued  at  half  a  million  dollars, 
shaped  so  as  to  fit  in  the  eye  socket  of  an  idol  in  India,  from  which  it 
was  stolen  by  a  French  soldier,  finally  purchased  by  Prince  Orloff 
who  sold  it  to  Catherine  II  of  Russia;  and  when  last  heard  of  it  was 
in  the  Winter  Palace,  Petrograd. 

Still  larger  is  the  Jubilee,  239  carats,  valued  at  two  million  dollars, 
found  in  South  Africa  in  1895,  and  now  in  England. 

The  largest  diamond  ever  found  was  the  Cullinan  (Plate  I), 
named  after  the  discoverer  of  the  Premier  Diamond  Mine,  South 
Africa.  It  was  picked  up  in  a  shallow  pit  in  that  mine  in  January, 
I9°5J  by  a  foreman,  who  was  given  ten  thousand  dollars  for  his  good 


22  GUIDE  TO  MINERAL  COLLECTIONS 

fortune  in  recognizing  it.  It  weighed  uncut  3,025!  carats,  or  about 
one  and  one-quarter  pounds,  and  was  valued  at  three  million  dollars. 
The  Transvaal  Republic  donated  it  to  King  Edward  VII  of  England, 
who,  it  was  hoped,  would  place  it  unaltered  in  a  museum  to  show 
for  all  time  the  largest  diamond  ever  found.  But  the  king  had  it 
cut  into  eleven  brilliants — four  of  which  are  yet  larger  than  any  others 
known.  Many  diamonds  smaller  than  those  mentioned  above  are 
interesting  because  of  their  history.  ' 

The  South  Star,  the  largest  diamond  found  in  Brazil  (in  1853) 
weighs  125  carats,  is  valued  at  four  hundred  thousand  dollars,  and 
is  now  owned  by  a  prince  in  Bztroda,  India. 

The  Shah  of  Persia,  86  carats,  now  in  Petrograd,  has  the  shape  of 
a  four-sided  prism  with  inclined  ends. 

No  diamond  has  had  a  more  varied  history  than  the  Sancy.  It 
was  found  in  India  and,  after  being  in  the  possession  of  Charles  the 
Bold,  who  lost  it  on  a  battlefield,  then  among  the  jewels  of  the  French 
Count  De  Sancy,  then  of  Queen  Elizabeth,  then  of  Louis  XIV,  then 
of  the  King  of  Spain,  and  then  of  a  Russian  Prince  Demidoff,  has 
again  been  taken  back  to  India  by  a  native  prince. 

All  of  the  above-named  are  beautiful  white  stones.  There  are 
some  colored  ones  greatly  prized,  as,  for  example,  the  yellow  Floren- 
tine and  the  blue  Hope  diamond.  The  Florentine,  found  in  India,  is 
now  among  the  Austrian  state  jewels,  after  having  been  owned  by 
Charles  the  Bold,  Pope  Julius,  and  the  Empress  of  Austria.  The 
Hope  diamond  is  the  most  famous  of  all  colored  stones.  It  is  of  a 
vivid  blue.  It  has  been  owned  by  wealthy  and  titled  people  in  Italy, 
France,  and  England,  and  now  is  in  the  possession  of  a  family  in 
Washington,  D.C. 

SUMMARY 

Diamond. — C.  Regular;  tetrahedrite  class  of  symmetry:  (m), 
(321);  supplementary  twins  of  tetrahedrons  and  contact  twins  on  (in). 
Cleavage  parallel  (in)  perfect;  brittle;  fracture  conchoidal. 

Hardness  =  i  o ;  gravity =3.52. 

Colorless,  yellow,  brown,  purple,  red,  blue;  luster,  greasy;  trans- 
parent ;  refraction  very  strong,  n  =  2 . 41 7 ;  dispersion  very  strong  =  o .  063. 

Infusible;   soluble  in  sulphuric  acid  and  potassium  bichromate. 

Australia,  South  America,  South  Africa. 


ELEMENTS  23 

Graphite 

Graphite  (ypafaiv,  "to  write"),  another  form  of  pure  carbon, 
though  not  abundant  in  Illinois,  is  scattered  in  flakes  through  gneisses 
and  other  rocks  which  have  been  strewn  over  the  state.  It  is  a  mineral 
so  useful  in  many  of  our  activities  that  it  could  not  be  spared.  What, 
for  example,  would  the  people  of  the  state  do  without  lead  pencils, 
lampblack,  stove  polish,  graphite  paints,  and  lubricants?  The 
specimens  on  exhibit  came  from  New  Jersey,  Ottawa,  Canada,  and 
Ceylon,  of  which  localities  the  last  has  yielded  the  greatest  quantities 
of  the  finest  quality. 

While  the  diamond  is  very  pronounced  in  its  shape,  graphite  is 
a  mineral  of  weak  molecular  attraction.  Its  external  form  is  not 
marked  and,  since  it  is  opaque  and  cannot  be  studied  under  the  micro- 
scope, there  is  even  some  doubt  as  to  what  its  system  of  crystallization 
really  is,  although  it  is  classified  as  hexagonal. 

Usually  it  occurs  in  leafy  or  scaly  flakes  disseminated  in  rocks 
that  originally  were  like  limestone  but  have  been  changed  by  heat 
into  marble  or  into  other  metamorphic  rocks.  Often  it  is  segregated 
into  compact,  granular,  or  earthy  masses  forming  veins  in  gneisses 
and  schists. 

While  diamond  is  the  hardest  of  substances,  there  is  no  mineral 
softer  than  pure  graphite;  while  diamond  is  transparent  and  of  light 
color,  graphite  is  opaque  and  black ;  while  diamond  is  a  non-conductor 
of  electricity,  graphite  is  a  good  conductor.  These  differences  are 
probably  due  to  different  arrangement  of  the  atoms  in  the  molecule, 
the  graphite  molecule  containing  three  atoms,  while  that  of  the 
diamond  contains  nine. 

Graphite  is  greasy  to  the  touch,  flexible,  i  in  hardness,  2  in  specific 
gravity,  infusible,  and  insoluble. 

Its  specific  heat  is  similar  to  that  of  the  diamond.  By  specific 
heat  is  meant  the  heat  required  to  raise  one  gram  of  a  substance 
through  one  degree  Centigrade.  Taking  as  the  unit  the  amount 
of  heat  required  to  raise  one  gram  of  water  one  degree  in  tempera- 
ture, graphite  requires  only  .12  and  diamond  .18  as  much. 

In  the  electric  arc,  diamond  can  be  converted  into  graphite  or 
graphite  to  diamond  by  varying  the  conditions. 

Graphite  is  chiefly  used  for  pencils,  stove  polish,  paint,  crucibles, 
and  lubricants.  In  early  days  only  the  purest  graphite  could  be 


24  GUIDE  TO  MINERAL  COLLECTIONS 

employed  for  "lead  pencils"  since  the  "leads"  were  cut  out  of  the 
solid  material.  Now  material  containing  much  foreign  matter  is 
pulverized  and  washed  to  free  it  from  impurities,  mixed  with  clay, 
and  burned.  The  amount  of  clay  used  and  the  heat  employed 
determine  the  degree  of  hardness  of  the  pencil.  Graphite  is  a  valuable 
paint  where  heat  is  to  be  resisted.  For  the  same  reason — because  of 
its  extreme  infusibility,  and  for  its  reducing  action,  i.e.,  its  tendency 
to  keep  oxygen  away  from  molten  metals — it  is  employed  for  crucibles. 
As  a  lubricant  it  is  useful  for  heavy  machinery  or  wherever  heat  would 
destroy  other  lubricants.  All  of  these  uses  are  well  illustrated  in  the 
graphite  case. 

SUMMARY 

Graphite. — C.  Hexagonal  (?);  in  plates,  scales,  masses.  Cleavage 
basal,  perfect;  flexible. 

Hardness=i;  gravity=2;  black;   streak  gray;   luster,  metallic. 

Ceylon,  Siberia,  Canada,  Mexico. 

Sulphur 

One  of  the  most  interesting  sights  in  one  of  America's  most  charm- 
ing parks — the  Yellowstone  National — is  a  group  of  hills,  the  highest 
of  which  rises  a  few  hundred  feet  above  the  surrounding  country  and 
is  called  "Sulphur  Mountain."  It  is  composed  of  siliceous  and  cal- 
careous material  mingled  with  vast  quantities  of  sulphur.  From  the 
yellowish-gray  mass  here  and  there  sulphurous  vapors  arise,  and  in 
many  places  sulphur  springs  burst  forth  and  run  in  rivulets  down  the 
side  of  the  hill,  leaving  behind  a  yellowish- white  trail.  In  many 
places  on  the  hill  the  sulphur  is  quite  pure,  earthy  in  character,  and 
yellowish-gray  in  color.  The  cavities  from  which  fumes  are  escaping 
are  often  lined  with  deposits  of  pure  yellow  sulphur  that  hang  in 
clustered  crystalline  masses  and  have  been  formed  by  the  sublimation 
of  sulphurous  vapors. 

Sublimation  deposits  characteristic  of  volcanic  regions  do  not 
furnish  fine  crystals  such  as  may  be  obtained  from  Sicily,  where  in 
the  marly  limestones  hot  waters  laden  with  sulphur  in  solution  have 
deposited  their  burden  under  favorable  conditions  and  produced 
large  crystals.  Samples  of  sulphur  from  the  Yellowstone  and  from 
Sicily  are  shown.  Illinois  occurrences  are  limited  to  whitish  masses 
remaining  from  decomposition  of  iron  sulphide  or  calcium  sulphate. 


ELEMENTS 


The  structure  of  the  sulphur  crystal  differs  from  that  of  a  diamond, 
since  sulphur  has  three  well-defined  directions  in  which  light,  heat, 
electricity,  and  various  chemical  reagents  act  with  different  ease  and 
rapidity.  Hence  a  sulphur  crystal  is  represented  by  three  axes  of 
different  lengths,  which  cross  each  other  at  right  angles.  These 
axes  characterize  the  Orthorhombic  System.  In  the  regular  system 
we  found  all  axes  equal;  in  the  orthorhombic  they  are  all  unequal. 
The  vertical  axis  c  may  be  greater  or  less  than  the  lateral  axis  b.  Of 
the  two  lateral  axes,  the  longer  is  always  chosen  as  the  b  axis  and  the 
shorter  as  a. 


FIG.  26. — Model  of  orthorhombic  bipyramid 


FIG.     2  7 . — Orthorhombic 
midal  plane  and  axes. 


pyra- 


Since  these  axes  represent  different  lengths  and  values,  they 
cannot  be  interchanged  as  they  were  in  the  regular  system.  Upon 
them  three  different  kinds  of  planes  may  be  constructed:  first,  those 
which  intersect  all  the  axes;  second,  those  which  intersect  two  axes 
and  are  parallel  to  the  third;  and  third,  those  which  intersect  one 
axis  and  are  parallel  to  two. 

i.  Planes  which  intersect  three  axes  are  called  pyramid  planes. 
They  correspond  to  the  octahedral  planes  of  the  regular  system. 
When  they  intersect  all  three  axes  at  unit's  distance,  the  typical 
bipyramid  results  (Fig.  26).  Figure  27  shows  the  construction  of 
the  pyramidal  plane. 


26 


GUIDE  TO  MINERAL  COLLECTIONS 


If  the  c  axis  is  intercepted  at  one-third  unit's  distance,  as  is  often 
the  case  with  some  planes  that  are  found  on  sulphur,  an  obtuse 

bipyramid     is     produced 
(Fig.  28). 

2.  Besides  pyramid 
planes  occur  the  so-called 
dome  planes  (from  domus, 
"  house,"  since  they  are 
like  a  roof).  They  inter- 
sect two  axes  and  are 
parallel  to  one  of  the 
lateral  axes  (Figs.  29-32). 

The  plane  which  is  paral- 
FIG.   28.— Obtuse  bipyramid  (113)  character-    lel  to  the  short  axig  ig  the 

istic  of  sulphur.  ,        -,      ,  , ,       u 

brachydome,  i.e.,  the  short 


FIG.  29. — Model  of  brachydomes  and 
macropincacoids. 


FIG.  30. — Upper  brachydome  planes 
(on). 


dome  (Figs.  29  and  30).  That  one  parallel  to  the  long  axis  is  called 
the  macrodome,  i.e.,  the  long  dome  (Figs.  31  and  32).  The  domes 
do  not  produce  closed  figures  unless  united  with  each  other  or  with 
some  other  planes.  In  Figures  29  and  31  they  are  closed  by  planes 
called  pinacoids. 

Prism  planes  (Fig.  33),  like  domes,  are  parallel  to  one  axis;  but 
it  is  always  the  c  axis  to  which  a  prism  is  parallel.  The  symbol  of 
the  prism  may  be  (no)  or  (210),  etc. 


ELEMENTS 


27 


3.  The  third  kind  of  planes  consists  of  those  parallel  to  two  axes 
and  intercepting  one  axis.     They  are  called  pinacoids  (from 
" plane")  (Figs.  34  and  35). 


1 


FIG.  31. — Model  of  macrodomes  and 


FIG.  32. — Upper  macrodomes  (101) 


brachy  pinacoids . 


The  basal  pinacoid,  or  base,  is  parallel 
to  a  and  b  and  intercepts  c  (ooi). 

The  brachypinacoid  (short  pinacoid) 
is  parallel  to  the  c  and  to  the  shorter  of 
the  two  lateral  axes,  the  a,  but  intercepts 
the  b  (oio).  The  macropinacoid  (long 
pinacoid)  is  parallel  to  c  and  to  the  longer 
of  the  lateral  axes,  but  intercepts  the  a 
(100). 

Figure  36  shows  a  combination  of 
prism  (no),  brachypinacoid  (oio),  and 
brachy  dome  (on). 

Pyramids,  domes,  prisms,  and  pina- 
coids complete  the  list  of  holohedral  forms 
in  the  orthorhombic  system. 

If  the  right-hand  upper  octant  of  a  pyramid  and  each  alternate 
octant  were  developed  at  the  expense  of  their  neighbors,  a  right-handed 
bisphenoid  would  be  produced  (Fig.  37).  A  left-handed  or  negative 
bisphenoid  would  result  if  the  left-hand  upper  octant  and  alternate 
octants  grew  at  the  expense  of  their  neighbors. 


FIG.  33. — Prism  (no)  and 
basal  (ooi)  planes. 


28 


GUIDE  TO  MINERAL  COLLECTIONS 


I 
I 

4-— 

i 


FIG.  34.— Base,  macropinacoid,  fie.  35.— Model  showing  base,  macro- 

and  brachypinacoid.  and  brachypinacoid. 


FIG.  36. — Model  of  prism 
(no),  brachypinacoid  (oio), 
and  brachydome  (on). 


FIG.     37. — Right-handed     sphenoid 
(in). 


ELEMENTS 


29 


In  sulphur  these  bisphenoids  (in)  are  commonly  united  and 
modified  by  basal  (ooi),  dome  (on),  and  obtuse  pyramid  planes 
(113)  (Figs.  38  and  39). 

In  Figure  39  the  left-handed  sphenoid  predominates  while  the 
right-handed  appears  as  a  very  small  plane.  In  Figure  38  they  are 
of  nearly  equal  size,  but  an  edge  instead  of  a  corner  where  the  a  and 
b  axes  are  intersected  shows  that  the  prevailing  form  is  not  a  bipyra- 
mid  but  rather  two  bisphenoids. 


-113 


FIG.  38. — Sulphur,  usual  habit 


FIG.  39. — Sulphur,  sphenoidal  habit 


Study  of  the  sulphur  crystal  has  shown  that  if  the  b  axis  is  taken 
as  unity,  the  a  axis  is  .8  and  the  c  is  1.9.  Therefore  to  construct 
the  various  planes  write  parameters,  ratios,  and  symbols  as  before. 


Ordinary  bipyramid  (Fig.  28) 
Obtuse  bipyramid  (Fig.  30) 

Brachydome  bipyramid  (Fig.  32) 
Macrodome  bipyramid  (Fig.  34) 
Prism  bipyramid  (Fig.  35) 


Similarly  for  the  pinacoids. 

If  melted  sulphur  is  quickly  cooled,  the  molecules  do  not  have 
opportunity  to  arrange  themselves  and  the  resulting  mass  is  without 


Parameters 

Ratios 

Symbols 

.8:1:1.9 

.8 

-1. 

1.9 

(ill) 

I 

* 

I 

.8 

i 

1  .9 

2.4:3:1.9 

(lI3) 

i 

*i* 

3 

oo  :i:i.9 

.8 

.1. 

i-9 

(on) 

o 

"x" 

i 

.8:00:1.9 

.8 

.  i  . 

1-9 

(xox) 

i 

'o' 

i 

.8:1:00 

.8 

I 

1-9 

(no) 

i 

'i' 

0 

£ 


30  GUIDE  TO  MINERAL  COLLECTIONS 

definite  form.  It  is  said  to  be  amorphous.  If  it  is  slowly  cooled, 
crystals  are  formed  similar  to  those  occurring  in  nature  but  differing 
in  this  respect,  that  they  slant  downward  parallel  to  the  a  axis,  so 
that  the  front  angle  between  the  c  and  a  axis,  /3,  is  greater  than 
90°  (Fig.  40).  The  basal  plane,  being  parallel  to  the  lateral  axes, 
slants  forward.  The  crystals  cannot  be  classed  in  the  orthorhombic 
system  but  are  in  the  monoclinic.  (Monoclinic  means  having  one 
inclination.)  After  a  time,  however,  these  monoclinic  crystals  become 
dull  and  fall  to  pieces,  since  their  molecules  tend  to  arrange  themselves 

in  the  more  stable  form  of  the  ortho- 

|C"  rhombic  crystal.     Orthorhombic  crys- 

I  tals  can    be    obtained    artificially  by 

I  allowing    sulphur    to   crystallize  from 

/3  ^  ^0°  i    '  solution  in  carbon  disulphide. 

(\/__  -~&r  Sulphur  cleaves  very  imperfectly, 

parallel  to  the  base  (ooi)  and  to  the 
prism  (no).  It  is  brittle  and  shows 
conchoidal  surfaces  when  broken. 
Hardness  =  2;  gravity  =  2;  luster, 
greasy,  resinous,  adamantine.  It  allows 

F.G.  4o.-Axes  of  a  monoclinic  1!ght  tO  PaSS  ^"^  ^perfectly,  i.e., 
crystal,  it  is  translucent.  Its  average  angle 

of  refraction  is  ^  =  2.04.  Since  the 

density  of  its  molecules  varies  in  different  directions,  a  ray  of 
entering  light  is  divided  into  two  rays.  These  rays  vibrate  at  right 
angles  to  each  other  and  are  differently  refracted.  The  dispersion 
or  difference  between  the  angle  of  greatest  and  least  refraction 
is  0.29. 

The  heat  conductivity  is  so  low  that  the  warmth  of  the  hand 
is  enough  to  cause  a  sulphur  crystal  to  crackle,  as  may  be 
noticed  when  a  crystal  is  held  near  the  ear.  Sulphur  becomes  elec- 
tric by  friction;  volatilizes  easily,  forming  sulphur  dioxide;  is 
insoluble  in  acids. 

Hundreds  of  thousands  of  tons  are  mined  in  Sicily  annually. 
Spain,  France,  and  Germany  produce  smaller  amounts.  Louisiana, 
Texas,  Nevada,  and  Utah  are  the  chief  source  of  the  domestic  supply. 
In  1916  the  first  two  states  supplied  98  per  cent  of  the  sulphur  ob- 
tained in  the  United  States. 


ELEMENTS  31 

SUMMARY 

Sulphur. — S.  Orthorhombic;  symmetry  holoaxial  (sulphur  class): 
(in),  (113),  (on),  (101),  (ooi). 

Cleavage  very  imperfect  (ooi),  (no);  brittle;  fracture  conchoidal. 

Hardness=2;  gravity  =2.  Yellow,  orarige,  white;  luster  resinous; 
translucent;  refraction  strong,  ^=2.04;  double  refraction  very  strong, 
positive. 

Fusible;  insoluble  in  acid;  soluble  in  carbon  disulphide. 

Sicily,  Spain,  France,  Germany,  Louisiana,  Texas. 

Arsenic 

A  small  mass  of  native  arsenic  from  Austria  represents  the  usual 
appearance  of  this  mineral.  It  somewhat  resembles  slag  from  a 
metal  furnace  or  some  kinds  of  lava,  since  it  shows  a  rounded,  twisted 
surface,  like  a  bunch  of  grapes  crowded  together,  and  is  dull  lead 
gray  or  blackish  on  the  surfaces  which  have  long  been  exposed  to  the 
air.  The  fresh  surfaces  are  tin  white  and  show  the  short  radiating 
needles  which  build  up  individual  portions  of  the  mass.  It  is  brittle, 
less  than  4  in  hardness,  and  5 . 7  in  specific  gravity. 

Native  arsenic  furnishes  but  little  of  the  arsenic  used  in  medicine 
and  the  manufacturing  arts. 

SUMMARY 

Arsenic. — As.  Hexagonal.  Cleavage  (oooi);  botryoidal,  reniform, 
massive;  brittle,  conchoidal. 

Hardness  =  3 . 5 ;  gravity  =5. 6.  Silver  white;  tarnishes  lead  gray  to 
black;  streak  white. 

Volatilizes  without  fusing,  tinges  flame  blue,  yields  dense  white  fumes; 
odor  of  garlic. 

Colorado,  Chile,  Saxony,  Austria. 

Antimony  and  Bismuth 

These  two  brittle  metals  are  very  similar  in  their  occurrence, 
properties,  and  uses.  They  do  not  develop  well-defined  crystals,  but 
are  usually  found  in  grains,  incrustations,  or  aggregations  of  scales 
which  form  masses.  Bismuth  is  sectile  and  is  the  softer  of  the  two, 
being  about  2  in  the  scale,  while  antimony  is  3.  Bismuth  is  the 
heavier  of  the  two,  having  a  specific  gravity  of  9,  while  that  of  anti- 
mony is  6.  Bismuth  is  somewhat  reddish  in  hue;  antimony  is  tin 


32  GUIDE  TO  MINERAL  COLLECTIONS 

white.  Both  are  metallic  in  luster,  soluble  in  nitric  acid,  easily 
fusible  and  volatile.  Both  are  found  in  association  with  silver, 
iron,  arsenic,  sulphur,  and  quartz.  One  hunting  for  these  minerals 
should  examine  crystalline  rocks. 

The  localities  most  noteworthy  on  account  of  specimens  of  anti- 
mony and  bismuth  are  Saxony,  Bohemia,  and  Japan.  Many  of  the 
ores  of  precious  metals  in  our  western  states  contain  these  metals. 

Antimony  and  bismuth  are  used  in  medicine  and  for  the  manu- 
facture of  alloys  for  type  metal,  babbitt  metal,  and  other  metals  of 
low  fusing-point. 

SUMMARY 

Antimony. — Sb.  Hexagonal;  symmetry  dihexagonal  alternating  (cal- 
cite  class).  Cleavage  parallel  (oooi)  perfect,  parallel  -%R  fair;  brittle; 
fracture  uneven. 

Hardness  =  3 .  5 ;    gravity  =  6. 6.     Tin  white;    luster  metallic;    opaque. 

Easily  fusible,  volatile;  oxidizes  in  nitric  acid. 

Germany,  France,  Japan,  Australia. 

Bismuth. — Bi.  Hexagonal;  symmetry  dihexagonal  alternating  (calcite 
class).  Cleavage  parallel  (oooi)  perfect,  parallel  -$R  fair;  sectile;  fracture 
hackly. 

Hardness=2;   gravity  =  9.     White  with  reddish  tinge;  luster  metallic. 

Easily  fusible;  volatilizes;  soluble  in  nitric  acid. 

Germany,  Bohemia,  Colorado. 

Gold 

Probably  there  is  more  general  interest  in  this  mineral  than  in 
any  other  that  is  found  in  the  earth's  crust. 

It  was  doubtless  the  first  metal  to  be  used  by  primitive  man, 
since  it  is  found  in  the  beds  of  streams  to  which  men  would  come  for 
water  and  which  were  their  highways  from  earliest  times.  Its  glitter 
would  attract  the  attention.  When  once  its  acquaintance  was  made, 
it  would  be  easily  recognized  again,  since  it  does  not  tarnish  or  rust, 
is  very  heavy,  being  19  times  as  heavy  as  water,  and  so  soft  and 
malleable  that  it  can  be  given  various  shapes  and  employed  in  many 
ways. 

These  qualities  would  lead  men  to  use  it  long  before  they  would 
notice  or  use  the  more  abundant  metals  such  as  iron.  It  is  found  in 
the  earliest  tombs,  such  as  those  at  Kertsch  in  the  Crimea,  in  northern 


ELEMENTS 


33 


Africa,  and  western  Asia.     Cloisonne  work  made  in  Egypt  three  or 
four  thousand  years  ago  shows  skill  in  the  use  of  gold. 

The  beauty  of  color,  ease  of  working,  weight  and  permanence  of 
gold,  render  it  a  mineral  of  great  value.  But,  however  great  its 
intrinsic  worth,  were  it  as  common  as  quartz,  for  example,  its  value 
would  be  decreased. 

Thus  is  it  over  all  the  earth 
That  which  we  call  the  fairest 
And  prize  for  its  surpassing  worth 
Is  always  rarest. 

Iron  is  heaped  in  mountain  piles 
And  gluts  the  laggard  forges, 
But  gold  flakes  gleam  in  dim  denies 
And  narrow  gorges. 

The  snowy  marble  flecks  the  land 
In  heaped  and  rounded  ledges, 
While  diamonds  hide  beneath  the  sand 
Their  starry  edges.1 

Gold  is  found  usually  in  quartz  veins,  in  pyrite  and  other  sul- 
phides, or  in  sands  and  gravels. 

In  quartz  it  occurs  as  fine  threads  or  thicker  wires  that  run 
singly  or  are  bunched  into  mossy 
or  treelike  masses  (arborescent). 
Sometimes  it  is  in  scales  or  grains 
isolated  at  times  or  packed  to- 
gether so  as  to  form  lenses  or 
nuggets.  Wiry  and  granular 
masses  alike  are  rounded,  twisted, 
and  so  distorted  as  to  give  little 
suggestion  of  crystal  faces.  How- 
ever, an  exposed  end  of  one  of 


1 


these    grains    or    threads,    one 

which   has   had   opportunity  to  FIG.  4i.— Cube 

develop  in  a  cavity  uncrowded 

by  quartz  or  some  other  mineral,  may  show  crystal  faces  clearly 

enough   developed  to  permit  of  study  and   to  make  possible   the 


1  J.  G.  Holland,  "Bitter  Sweet." 


34 


GUIDE  TO  MINERAL  COLLECTIONS 


conclusion  that  the  structure  of  gold  agrees  with  that  of  the 
diamond,  the  molecules  being  so  arranged  as  to  place  it  in  the  regular 
system.  , 

Besides  the  octahedron  (m),  two  other  forms  appear,  namely, 
the  cube  (100)  (Fig.  41)  and  the  four-sided  cube  (tetrahexahedron, 
210)  (Figs.  42  and  43).  To  construct  the  cube,  write  the  notation 
as  before.  Since  the  axes  are  interchangeable,  six  planes  will  be 
produced.  The  parameters  of  the  front,  right  side,  and  top  are  as 
follows: 


Parameters 

i :  oo  :  oo 


oo  : i: oo 


oo  ;  oo  ;  i 


Ratios 
III 

1*0*0 

III 

o'i'o 
III 
I'Q'I 


Symbols 

(100) 
(oio) 
(ooi) 


A  cube  with  four  faces  in  each  cubic  face  (Figs.  42  and  43)  results 
when  one  of  the  three  axes  is  intersected  at  twice  unit's  distance,  for 
example. 

Ratios 
III' 
2'l'o 
III 

I  '  2'  O 
III 
O'2'l 
III 
O*I*2 

II  I 
2'o'l 
III 
I*O*2 


Parameters 
i:2:oo 


oo  11:2 


2  :  oo  :  i 


Symbols 
(210) 

(120) 
(021) 
(012) 
(201) 
(102) 


Gold  crystals  are  usually  small,  distorted,  and  so  grouped  that 
to  study  and  decipher  them  is  a  difficult  matter.  The  gold  contained 
in  pyrites  and  metallic  sulphides  is  so  finely  divided  as  to  be  invisible. 
It  is  mechanically  included  in  the  sulphides  and  not  chemically  united 
with  the  sulphur.  In  nearly  every  country  in  which  gold  is  mined,  it 


ELEMENTS 


35 


was  first  discovered  in  sands  and  gravels,  and  such  deposits  until 
within  the  last  fifty  years  have  been  the  chief  source  of  the  metal. 

Like  diamonds,  gold  has  been  able  to  withstand  the  friction  to 
which  it  was  subjected  while  being  washed  from  the  original  ledge. 
Diamonds  resisted  the  friction  because  of  their  hardness ;  gold  because 
of  its  tenacity;  both  have  endured  because  of  their  insolubility 
and  slight  affinity  for  oxygen.  The  condition  of  gold  in  alluvial 
deposits  varies  from  dust  of  microscopic  fineness  to  nuggets  many 
pounds  in  size.  In  California  a  nugget  weighing  161  pounds  was 


FIG.  42. — Tetrahexahedron  model 


FIG.  43. — Construction  of  tetrahexa- 
hedron. 


found.  The  largest  nuggets  have  been  discovered  in  Australia,  three 
weighing  over  200  pounds  having  been  found  there.  The  largest  of 
them,  the  "  Welcome,"  weighed  248  pounds. 

The  origin  of  nuggets  of  such  size  has  been  a  matter  of  much 
speculation,  since  no  masses  of  similar  size  have  been  found  in  veins. 
It  has  been  suggested  that  small  particles  carried  downstream  were 
welded  together  by  the  impact  of  water-tossed  gravel  until  a  large 
nugget  was  formed,  or  that  the  nuggets  have  grown  by  accretion  of 
gold  from  some  percolating  solution.  Polished  and  etched  surfaces 
of  nuggets,  however,  show  crystalline  structure.  This  would  be 
wanting  in  welded  gold,  and  there  is  an  absence  of  the  onion-like 
structure  that  would  be  expected  if  the  gold  were  deposited  by  accre- 
tion from  solution.  Hence  it  may  be  concluded  that  the  nuggets 


36  GUIDE  TO  MINERAL  COLLECTIONS 

were  originally  in  quartz  veins  and  have  been  rounded  in  the  down- 
ward journey  from  some  high  ledge  to  the  resting-place  in  which  they 
were  discovered. 

As  to  the  origin  of  gold,  nothing  is  known.  The  same  may  be 
said  in  regard  to  all  elements.  All  that  is  known  is  something  of  the 
method  of  their  transference  and  deposition.  Light  is  shed  on  the 
subject  by  the  fact  that  many  fresh  waters  and  all  sea  waters  contain 
gold  in  appreciable  quantities.  There  is  nearly  one  grain  of  gold 
(five  cents'  worth)  in  every  ton  of  ocean  water.  Then  in  all  the  oceans 
there  is  about  seventy-five  billion  dollars'  worth. 

Gold  in  solution,  possibly  as  a  telluride,  chloride,  or  cyanide,  was 
carried  by  waters  and  deposited  by  them  upon  neutralization,  cool- 
ing, or  evaporation.  Though  the  surfaces  of  gold  crystals  are  rounded 
and  often  look  as  if  melted,  their  appearance  is  not  due  to  fusion  but  to 
their  manner  of  crystallization.  The  origin  of  the  gold  is  the  same  as 
the  origin  of  the  vein  material  inclosing  it — quartz,  fluorite,  and  calcite. 
All  of  these  minerals  are  commonly  deposited  from  aqueous  solutions. 

Gold  melts  at  1200°  C.  and  forms  such  perfectly  spherical  globules 
that  by  microscopical  measurements  it  is  possible  to  estimate  the 
amount  of  gold  in  a  globule  and  hence  to  dispense  with  fine  balances 
in  assaying.  Gold  is  soluble  in  aqua  regia  only  (a  combination  of 
nitric  [HNO3]  and  hydrochloric  [HC1]  acids). 

Sulphur  and  oxygen  do  not  unite  with  gold,  and  hence  it  remains 
bright  in  nature  or  when  worn  as  an  ornament. 

All  gold  contains  silver  in  solid  solution.  As  the  amount  of  silver 
increases,  the  alloy  becomes  paler,  lighter,  and  more  liable  to  dissolve 
in  nitric  acid.  Most  Hungarian  gold  contains  30  per  cent  of  silver, 
California  gold  10  per  cent,  Australian  gold  (Mount  Morgan,  Queens- 
land), reputed  to  be  the  purest,  only  .3  per  cent. 

Platinum,  copper,  and  iron  minerals,  calcite,  fluorite,  quartz, 
feldspar,  amphibole,  and  pyroxene,  mica,  garnet,  and  zircon,  are  the 
minerals  most  usually  found  with  gold. 

The  rocks  in  which  gold-bearing  veins  are  found  are  igneous 
rocks  such  as  granites,  syenites,  and  porphyries;  or  metamorphic 
rocks  such  as  gneisses  and  schists.  The  richest  veins  are  usually  at 
places  of  contact  of  different  kinds  of  rock. 

California,  Nevada,  Colorado,  Montana,  and  South  Dakota  have 
been  the  chief  producers  of  gold  in  this  country  since  the  discovery  of 


ELEMENTS  37 

the  metal  in  California  in  1848.  The  only  gold  found  in  Illinois  is  an 
occasional  piece  contained  in  some  rock  transported  from  northern  re- 
gions by  the  glaciers  of  Pleistocene  times.  There  are  no  deposits  of 
commercial  importance.  In  spite  of  this  fact,  the  procession  of  people 
who  hope  to  discover  such  deposits  or  think  they  have  done  so  will 
never  end.  They  bring  to  the  museum  iron  sulphide  (pyrite),  decay- 
ing mica  (vermiculite),  and  other  minerals,  confident  that  they  have 
found  valuable  deposits  of  precious  metal;  and  when  disillusioned  are 
dejected.  At  one  time  the  United  States,  at  another  time  South  Africa, 
leads  the  world  in  gold  production,  while  Australia  ranks  third. 

Gold  is  a  metal  useful  in  all  places  where  hardness  and  toughness 
are  not  desired  but  where  insolubility,  permanence  in  the  air,  beauty 
of  color,  softness,  and  ductility  are  sought.  Since  the  earliest  times 
it  has  been  used  for  personal  adornment  and  for  ornaments  for  the 
home,  the  church,  and  the  palace.  It  is  universally  favored  as  a 
medium  of  exchange. 

SUMMARY 

Gold. — Au.  Regular;  holosymmetric;  distorted  (in),  (100),  (210); 
fibers,  plates,  grains.  Malleable;  ductile;  fracture  hackly. 

Hardness  =  2.5;  gravity  =  19.3.     Gold  yellow,  metallic,  opaque. 

Fusible  at  1200°  C.;  soluble  in  aqua  regia. 

Western  North  and  South  America,  South  Africa,  Australia. 

Silver 

Silver  resembles  gold  in  its  mode  of  occurrence,  crystal  habit,  and 
physical  properties.  Chemically  it  is  not  so  stable  as  gold,  being 
readily  affected  by  acid  fumes  and  liquids.  It  is  rarely  found  in 
placer  deposits,  but  occurs  most  commonly  in  wiry,  mossy,  flaky,  or 
granular  forms  in  veins. 

Sometimes  large  pure  masses  are  discovered.  One  of  the  most 
famous  was  an  eight-hundred-pound  mass  found  in  Peru.  Another 
from  Kongsberg,  Norway,  weighing  five  hundred  pounds,  is  preserved 
in  Copenhagen. 

Crystals  of  silver  are  usually  so  distorted  that  their  form  is 
difficult  to  decipher,  but  under  favorable  circumstances  octahedrons 
(in),  cubes  (100),  and  tetrahexahedrons  (210)  can  be  distinguished. 

Like  gold,  silver  has  no  direction  of  easy  separation  (cleavage). 
When  broken,  the  fractured  surfaces  are  splintery.  It  is  inferior  to 


38  GUIDE  TO  MINERAL  COLLECTIONS 

gold  in  its  malleability  and  ductility,  as  it  is  possible  only  to  beat 
leaves  of  it  so  thin  that  it  requires  one  hundred  thousand  leaves  to 
form  a  pile  one  inch  in  height,  and  one  grain  can  be  drawn  out  into 
four  hundred  feet  of  wire.  Gold,  however,  can  be  beaten  into  leaves 
thin  enough  to  require  two  hundred  and  eighty-two  thousand  leaves 
to  form  an  inch-high  pile,  and  one  grain  can  be  drawn  into  five 
hundred  feet  of  wire. 

Silver  is  unsurpassed  as  a  conductor  of  electricity.  Its  conduc- 
tivity is  placed  at  100  per  cent,  that  of  copper  at  93  per  cent,  and 
platinum  at  16  per  cent. 

One  thousand  degrees  Centigrade  of  heat  are  required  to  melt  it. 
When  fused  it  can  absorb  twenty  times  its  bulk  of  oxygen,  which  it 
gives  off  upon  cooling,  causing  it  to  blossom  into  arborescent  forms. 

It  is  readily  soluble  in  nitric  acid.  It  unites  with  sulphur  so 
easily  that  to  keep  silver  bright  is  a  very  difficult  task. 

The  chief  source  of  the  metal  is  not  native  silver  but  sulphides 
such  as  argentite,  proustite,  tetrahedrite,  etc.,  minerals  which  will 
be  described  later. 

The  association,  occurrence,  and  localities  of  silver  are  nearly 
identical  with  those  of  gold. 

The  United  States  has  for  many  years  been  one  of  the  principal 
producers,  as  well  as  the  chief  consumer,  of  silver. 

It  is  estimated  that  the  ocean  contains  over  two  million  tons  of 
silver  worth  more  than  $38,000,000,000. 

Silver  is  used  extensively  for  coinage,  for  making  household 
articles,  for  photographic  purposes,  and  in  various  other  ways. 

SUMMARY 

Silver. — Ag.  Regular,  holosymmetric ;  (100),  (210),  (in);  twinned  on 
(in).  Threads,  wires,  plates,  grains,  masses.  Malleable;  ductile;  fracture 
hackly. 

Hardness  =  2.5;  gravity  =  10.  5.     White,  metallic,  opaque. 

Fusible  at  1050°  C. ;  soluble  in  nitric  acid. 

Cordilleran  states  in  both  North  and  South  America,  Australia,  Ger- 
many. 

Copper 

Copper  is  similar  in  its  physical  characteristics,  association,  and 
occurrence  to  the  two  minerals  just  described,  but  is  more  abundant. 


PLATE  IV 


Dendritic  copper  from  Calumet  and  Hecla  mining 
region,  Michigan. 


ELEMENTS 


39 


In  the  rare  crystal  faces  discernible,  possibly  the  tetrahexahedron 
(210)  and  dodecahedron  (no)  (Fig.  44)  are  more  common  than  they 
are  in  gold  and  silver.  The  dodecahedron  (no)  can  be  constructed 
from  the  following  parameter  (Fig.  45) : 


Parameter 

1:1:00 


Ratios 
III 
1*1*0 


Symbols 

(no) 


Wiry  and  arborescent  forms  are  common.     Masses  of  remarkable 
size  have  been  found.     One  of  the  largest  was  45  feet  long  and 
weighed  420   tons.     It  was  found   in   the   " Minnesota   Mine"   in 
Michigan.     That  region  has 
produced  more  pure  copper 
than  any  other  in  the  world. 
The  copper  is  disseminated 
in    breccias,    conglomerates, 
and  basalts,  or  is  collected  in 
veins  of  calcite,  fluorite,  anal- 
cite,  and  quartz  which  pene- 
trate   the    basalt.     Often    a 
cavity   is  filled   partly  with 
copper  and  partly  with  silver. 
If  these  metals  had  been  de- 
posited from  a  fused  mass, 
they  would  have  been  united 
in  an  alloy  rather  than  stand- 
ing side  by  side.     Evidently  FlG.  44._Model  of  a  dodecahedron 
they   were   formed    from    a 

solution,  and  the  more  difficultly  soluble  silver  was  first  deposited 
and  later  the  copper. 

Copper  is  redder  than  gold  and  much  more  soluble.  It  is  one  of 
the  most  useful  of  metals,  being  used  for  electrical  purposes  and  for 
many  domestic  and  commercial  articles. 

The  United  States  has  produced  about  three  times  as  much 
copper  as  the  rest  of  the  world  together.  Arizona,  Montana,  and 
Michigan  are  the  leading  states  in  production.  In  the  two  former 
the  ores  are  chiefly  sulphides  and  carbonates;  in  Michigan,  native 
copper. 


GUIDE  TO  MINERAL  COLLECTIONS 


Glacial  drift  from  the  north  has  brought  nuggets  of  copper,  some 
of  them  weighing  more  than  50  pounds,  and  scattered  them  widely 
over  Illinois.  One  (No.  695)  found  in  the  drift  in  Peoria  County 
weighs  i8f  pounds.  A  hole  was  cut  through  it  by  the  finder  so  that 

it   could  be   used  on   a 

C  rope    to    close    a    gate. 

No.  693  from  Macon 
County  weighs  17  f 
pounds  and  is  covered 
with  the  fine  green  de- 
posit with  which  time 
paints  old  copper  domes 
of  churches  and  palaces. 
This  deposit  is  formed 
when  carbon,  oxygen, 
and  water  unite  with 
copper  to  produce  the 
copper  carbonate  called 
malachite.  No.  3383  is 
an  irregular  nugget  (n| 
pounds)  which  shows 
the  scratches  made  by 
the  rocks  over  which  the 
nugget  was  pushed  while  frozen  in  a  glacier.  No.  259,  a  small  nugget 
from  Jersey  County,  was  found  farthest  south  of  any  specimen  in 

the  collection. 

SUMMARY 

Copper. — Cu.    Regular,  holosymmetric;  elongated  (210);   twinned  on 
(in);  threads,  wires,  masses.     Malleable;  ductile;  fracture  hackly. 
Hardness  =2.5;  gravity =8.9.     Copper  red,  metallic,  opaque. 
Fusible  at  1100°  C.,  soluble  in  nitric  acid. 
Michigan,  Arizona,  New  Mexico. 

Mercury 

Mercury  is  the  only  element  which  is  liquid  at  ordinary  tempera- 
ture. It  solidifies  at  —  40°  C.  and  in  so  doing  crystallizes  in  the 
regular  system.  It  unites  so  readily  with  sulphur  that  it  is  rarely 
found  uncombined  with  that  element.  Cinnabar,  HgS,  is  the  chief 
source  of  the  metal. 


FIG.  45. — Construction  of  a  dodecahedron 


ELEMENTS  41 

Mercury  is  used  in  making  medicine,  in  "silvering"  mirrors,  and 
in  the  manufacture  of  toys,  but  chiefly  as  a  means  of  collecting  finely 
divided  gold  in  placer  mining  and  in  the  free  milling  process. 

About  the  same  time  that  gold  was  discovered  in  California, 
fortunately  quicksilver  was  found  at  New  Almaden,  some  fifty  miles 
south  of  San  Francisco. 

The  United  States  is  at  present  the  leading  country  in  the  pro- 
duction of  cinnabar,  from  which  mercury  is  obtained.  The  famous 
old  Spanish  localities  now  take  second  rank.  Nature  has  not  provided 
any  deposits  of  mercury  in  Illinois.  Nor  do  we  need  it  as  much  as 
do  some  other  states. 

SUMMARY 

Mercury. — Hg.     Liquid,  amorphous;  at  —40°  C.    Regular. 
Gravity  =15.     White,  metallic,  opaque. 
Volatilizes,  sublimes. 
California,  Spain. 

Platinum 

Platinum  is  a  steel-gray,  metallic,  moderately  hard,  exceedingly 
heavy  mineral  occurring  in  small  flat  grains  in  alluvial  deposits.  The 
world's  supply  has  been  obtained  practically  from  the  Ural  Mountains 
alone.  If  its  appearance  and  characteristics  were  more  widely  known 
among  prospectors,  other  localities  might  be  added  to  •  the  list  of 
producers. 

Because  of  its  peculiar  utility  and  rarity,  platinum  is  at  present 
unsurpassed  in  commercial  value  by  any  metal.  Its  especial  useful- 
ness depends  upon  its  resistance  to  heat.  Over  2000°  C.  are  required 
to  melt  it.  This,  in  addition  to  its  insolubility,  makes  it  serviceable 
for  dental  purposes,  for  crucibles,  wire,  and  foil  to  be  used  in  chemical 
laboratories  and  manufacturing  plants  and  for  electrical  purposes. 
The  attempt  to  find  some  metal  which  will  take  the  place  of  plati- 
num has  been  unsuccessful. 

The  United  States  uses  about  half  of  all  the  platinum  produced 
in  the  whole  world. 

The  crystal  form  of  platinum,  being  similar  to  that  of  gold,  silver, 
and  copper,  presents  nothing  new  for  consideration. 

Platinum  is  very  finely  disseminated  in  gravels  derived  from  ser- 
pentine and  syenite,  and  large  placers  may  be  expected  only  in  very 


42  GUIDE  TO  MINERAL  COLLECTIONS 

old  land  areas  which  have  been  subjected  to  protracted  degradation. 
The  Ural  Mountains  furnish  such  conditions. 

Small  percentages  of  platinum  are  often  obtained  from  sulphides  of 
antimony,  arsenic  and  copper,  and  in  chromite.  The  placers  of  the 
Ural  Mountains,  Columbia,  and  California  contain,  associated  with 
platinum,  other  minerals  of  high  specific  gravity  such  as  gold,  cas- 
siterite,  magnetite,  hematite,  chromite,  and  rutile. 

SUMMARY 

Platinum. — Pt.  Regular;  holosymmetric ;  grains  and  nuggets.  Malle- 
able; ductile;  fracture  hackly. 

Hardness  =  4.5;  gravity=i9;  chemically  pure,  21.    Steel  gray. 

Infusible;  soluble  in  nitre-hydrochloric  acid  (aqua  regia). 

Nijni  Taguilsk  (Urals) ;  Columbia,  South  Africa,  Canada,  Wyoming, 
California. 

Iron 

Iron  so  readily  unites  with  oxygen,  sulphur,  and  other  elements 
that  it  rarely  occurs  native.  Consequently,  while  minerals  contain- 
ing iron  are  numerous  and  abundant,  pure  iron  is  rare.  Yet  it  is 
one  of  the  most  interesting  of  minerals  because  of  its  origin.  Some 
of  it  is  terrestrial  and  some  meteoric  in  origin. 

Terrestrial  iron  is  found  as  small  imbedded  particles  in  basalt, 
peridotite,  and  serpentine — three  kinds  of  dark  rocks  abundant  in 
many  mountain  regions — and  in  deposits  derived  from  the  disinte- 
gration of  these  rocks.  Gold  and  platinum  are  usually  associated  with 
terrestrial  iron. 

At  several  places  on  the  west  coast  of  Greenland,  especially  at 
Disco  Island,  large  masses  of  iron  occur  which  are  regarded  as  origi- 
nating from  deep-seated  portions  of  the  earth,  since  the  basalts  of  the 
region  contain  scattered  grains  and  globules  of  iron. 

Meteoric  iron  illustrates  the  fact  that  the  science  of  mineralogy  is 
concerned  not  only  with  this  earth  but  with  the  universe  as  well. 

Until  within  the  last  one  hundred  years  the  idea  prevailed  that 
meteorites  were  portions  of  this  earth  which  had  been  thrown  out  of 
volcanoes  with  such  velocity  as  to  reach  great  heights  and  then  to 
fall  back  with  enormous  speed.  But  as  the  composition  of  meteorites 
became  known  and  the  circumstances  connected  with  their  fall  were 
investigated,  students  of  the  subject  were  convinced  that  they  are 
fragments  of  other  heavenly  bodies — the  dust  of  the  universe. 


PLATE  V 


Mukerop  meteorite,  one-sixth  natural  size. 
on  page  44  was  cut  from  the  center  of  this  mass. 


Fell  in  Amalia-Goamus,  West  Africa.     Section  mentione 


ELEMENTS  43 

Myriads  of  them  enter  the  earth's  atmosphere.  At  night  they 
are  seen  to  flash  in  the  heavens  when  they  are  ignited  by  the  friction 
generated  in  their  fall  through  the  earth's  atmosphere.  Many  enter 
the  atmosphere  at  such  an  angle  that  they  leave  it  without  touching 
the  earth;  many  are  totally  consumed  as  they  fall;  some  reach  the 
earth's  surface  as  cosmic  dust,  as  grains,  or  even  as  masses  many  tons 
in  weight.  In  1894  at  Cape  York,  in  the  northern  part  of  Green- 
land, a  mass  weighing  36  tons  was  found  and  three  years  later  brought 
by  R.  E.  Peary  to  New  York  City.  It  was  called  by  the  Eskimos 
"Ahnighito"  or  "The  Tent." 

Occasionally  a  meteorite  has  been  seen  as  it  fell  and  has  been 
picked  up  while  still  warm.  Those  which  have  been  observed  in 
the  air  and  then  found  are  called  "  falls."  Their  number  is  less 
than  the  so-called  "  finds,"  which  are  not  seen  to  fall  but  are  simply 
picked  up.  Several  hundred  " falls"  and  "finds"  have  been  collected 
and  described. 

A  meteorite  entering  the  atmosphere  may  have  an  astonishingly 
high  velocity — something  like  45  miles  a  second — but  because  of  the 
resistance  of  the  air  be  reduced  in  velocity  and  strike  the  earth's  sur- 
face with  small  force.  Meteoric  stones  fell  upon  the  ice  at  Hessle, 
Sweden,  and  rebounded  without  either  breaking  the  ice  or  being 
themselves  shattered.  The  heat  generated  by  the  friction  with  the 
air  fuses  the  surface  of  the  meteorite,  especially  on  the  front  side,  and 
causes  the  melted  material  to  flow  back  in  waves,  making  a  kind  of 
"varnish."  Meteorites  are  usually  pitted  with  thumblike  impres- 
sions. Since  the  heating  is  sudden,  the  surface  may  be  fused  while 
the  interior  is  still  cold.  The  unequal  expansion  causes  them  to 
explode  with  loud  report  and  to  scatter  over  wide  territory. 

According  to  constitution  there  are  three  kinds  of  meteorites: 
first,  those  consisting  almost  wholly  of  iron  (siderites) ;  second,  those 
having  a  cellular  matrix  of  iron  in  which  stony  matter  is  imbedded 
(siderolites) ;  and  third,  those  composed  almost  entirely  or  wholly  of 
stony  matter  (aerolites). 

Meteoric  iron  is  massive,  but  its  crystalline  structure  can  be 
readily  discerned  when  it  is  etched  with  diluted  nitric  acid,  since 
triangular  markings  usually  appear  on  the  surface.  They  are  due  to 
the  presence  of  nickel.  The  form  and  the  widths  of  the  bands 
depend  upon  the  percentages  of  nickel  present.  The  figures  resulting 


44  GUIDE  TO  MINERAL  COLLECTIONS 

are  called  Widmanstatten  figures,  after  the  man  who  first  studied 
them. 

The  largest  meteorite  ever  discovered  in  the  United  States  and 
one  of  the  most  interesting  is  the  Willamette  iron.  It  was  found 
19  miles  south  of  Portland,  Oregon,  in  1902.  It  weighs  15  tons  and 
is  now  in  the  American  Museum  of  Natural  History. 

Meteorites  have  been  found  in  our  neighboring  states,  Michigan, 
Indiana,  Kentucky,  Missouri,  Iowa,  and  Wisconsin,  but  thus  far  not 
a  single  example  has  been  reported  in  Illinois.  All  accounts  of  the 
finding  of  meteorites  in  this  state  have  upon  investigation  proved  to 
be  untrue.  There  appears  to  be  no  reason  why  falls  may  not  occur 
here  at  any  time.  If  people  are  more  observant,  we  may  some  time 
discover  and  preserve  these  messengers  from  the  great  waste  spaces. 

The  largest  meteorite  exhibited  in  the  collection  (No.  4064)  is  a 
1-inch- thick  section  from  13  to  15  inches  in  diameter  and  weighing 
13!  pounds  avoirdupois.  It  was  cut  from  the  Mukerop  meteorite 
which  fell  in  southwestern  Africa  (Plate  V).  The  following  also  are 
shown:  a  dozen  examples  of  the  Canon  Diablo,  Arizona,  meteorite 
(No.  3385);  about  fifty  of  the  Holbrook,  Arizona;  one  from  Eddy 
County,  New  Mexico  (Sacramento  Mountains,  No.  3384);  Sheridan 
County3  Kansas  (Saline,  No.  4106);  Lyon  County,  Kansas  (Admire, 
No.  4104);  Phillips  County,  Kansas  (Long  Island,  No.  4109); 
Iowa  County,  Iowa  (Homestead,  No.  4107,  and  Forest,  No.  4108); 
Emmet  County,  Iowa  (No.  1730);  Bullitt  County,  Kentucky  (Salt 
River,  No.  4103);  Kent  County,  Michigan  (Grand  Rapids,  No. 
4103);  and  state  of  Mexico,  Mexico  (Toluca,  No.  4101). 

SUMMARY 

Iron. — Fe.     Nickel  usually  present.     Regular;    (in),  (100);    massive 
lamellar;   cleavage  parallel  (100)  perfect;  malleable;   fracture  hackly. 
Hardness  =  4.5;    gravity=7.5.     Gray  to  black,   metallic,   magnetic 
Infusible;  soluble  in  acid. 
Greenland,  and  in  meteorites  of  wide  distribution. 


ELEMENTS 


45 


LIST  OF  ELEMENTS  AND  THEIR  ATOMIC  WEIGHTS 


Name 


Combining  Weight 
Oxygen  =  1 6 

Aluminium,  Al 27 

Antimony,  Sb 1 20 

Argon,  Ar 39 

Arsenic,  As 75 

Barium,  Ba 137 

Beryllium,  Be 9 

Bismuth,  Bi 208 

Boron,  B . . . 1 1 

Bromine,  Br 79 

Cadmium,  Cd 112 

Caesium,  Cs 132 

Calcium,  Ca 40 

Carbon,  C 12 

Cerium,  Ce 140 

Chlorine,  Cl 35 

Chromium,  Cr 52 

Cobalt,  Co 59 

Columbium,  Cb 94 

Copper,  Cu 63 

Dysprosium,  Dy 162 

Erbium,  Er 167 

Europium,  Eu 152 

Fluorine,  F 19 

Gadolinium,  Gd 157 

Gallium,  Ga 70 

Germanium,  Ge 72 

Glucinum,  Gl 9 

Gold,  Au 197 

Helium,  He 4 

Hydrogen,  H i 

Indium,  In 114 

Iodine,  1 127 

Iridium,  Ir 193 

Iron,  Fe 56 

Krypton,  Kr • 83 

Lanthanum,  La 139 

Lead,  Pb 207 

Lithium,  Li 7 

Lutecium,  Lu 1 74 

Magnesium,  Mg 24 

Manganese,  Mn 55 


Name 


Combining  Weight 
Oxygen  =  1 6 


Mercury,  Hg 200 

Molybdenum,  Mo 96 

Neodymium,  Nd 144 

Neon,  Ne 20 

Nickel,  Ni 59 

Nitrogen,  N 14 

Osmium,  Os 191 

Oxygen,  O 16 

Palladium,  Pd 107 

Phosphorus,  P 31 

Platinum,  Pt 195 

Potassium,  K 39 

Praeseodymium 141 

Radium,  Ra 226 

Rhodium,  Rh 103 

Rubidium,  Rb 85 

Ruthenium,  Ru. 102 

Samarium,  Sm 150 

Scandium,  Sc 44 

Selenium,  Se 79 

Silicon,  Si 28 

Silver,  Ag 108 

Sodium,  Na 23 

Strontium,  Sr 88 

Sulphur,  S 32 

Tantalum,  Ta 181 

Tellurium,  Te 127 

Terbium,  Tb 159 

Thallium,  Tl 204 

Thorium,  Th 232 

Thulium,  Tu 168 

Tin,  Sn 119 

Titanium,  Ti 48 

Tungsten,  W 184 

Uranium,  U 239 

Vanadium,  V 51 

Xenon,  Xe 131 

Ytterbium,  Yt 172 

Yttrium,  Y 89 

Zinc,  Zn 65 

Zirconium,  Zr 91 


CLASS  II.     SULPHIDES 

The  next  group  of  minerals  which  would  naturally  claim  the 
attention  of  the  visitor  is  that  which  embraces  minerals  consisting  of 
a  mixture  of  sulphur  with  some  metal  like  antimony,  molybdenum, 
lead,  silver,  copper,  zinc,  mercury,  or  iron. 

From  the  twenty-five  or  more  minerals  in  the  group,  thirteen  are 
common;  and  while  but  eight  of  them  are  found  in  Illinois,  all  are 
used  here  and  all  are  of  interest,  since  they  show  marked  properties. 

They  are  stibnite,  molybdenite,  galena,  argentite,  chalcocite, 
sphalerite,  cinnabar,  pyrrhotite,  erubescite,  chalcopyrite,  pyrite, 
marcasite,  and  arsenopyrite. 

Stibnite 

Stibnite,  a  sulphide  of  antimony  (Sb2S3)  is  the  chief  source  of  the 
metal,  antimony.  Its  crystals  are  often  large  and  beautiful.  They 
resemble  sulphur  crystals  since  their  structure  is  different  in  three 
directions.  The  planes  which  are  usually  developed  are  prisms  and 
pinacoids.  Several  pyramid  planes  are  of  common  occurrence.  The 
crystals  are  holohedral.  Basal  planes  are  wanting.  The  long  needle- 
like  crystals  often  terminate  in  a  flat  pyramid  (113),  as  shown  in 
Figure  46.  The  ratio  of  the  axes  a:b:c  is  .99:  i  :  i  .01,  differing  thus 
but  slightly  from  a  mineral  in  the  regular  system. 

Applying  these  values  and  using  the  parameter  as  usual,  the 
following  result: 

Parameters  Ratios  Symbols 

.OQ    I    I  .  OI 

2.97:3:1.01  ::  ("3) 


.00    I     I.OI  /          N 

oo  :i;oo  (oio) 

o   'i'    o 

Some  crystals  of  stibnite  are  of  remarkable  size  and  beauty.  One 
of  the  finest  specimens  in  any  museum  may  be  seen  in  the  British 
Museum.  It  is  a  group  of  crystals  eighteen  inches  long  and  termi- 
nated by  lustrous  pyramid  faces.  It  came  from  the  antimony  mines 

46 


PLATE    VI 


a,  Stibnite,  Japan 


b,  Molybdenite  from  Aldfield,  Pontiac  County, 
Quebec,  Canada. 


SULPHIDES 


47 


at  Shikoku,  Japan,  a  locality  which  has  furnished  a  larger  number  of 
remarkable  specimens  than  any  place  in  the  world.  Our  largest 
specimen,  No.  3784  (Plate  VI  a),  comes  from  the  same  place.  Other 
samples  are  from  Portugal,  Australia,  and  the  western  United  States. 
Stibnite  crystals  are  often  twisted,  curved,  and  warped.  The  most 
usual  occurrence  is  that  of  massive  forms  with  bladelike  or  fibrous 
structure. 

The  mineral  cleaves  easily  parallel  to  the  brachypinacoid,  and 
shows  nicks  and  horizontal  lines  at  right  angles  to  the  c  axis,  indi- 
cating " glide  planes"  parallel  to  the  base  (ooi).  These  glide  planes 
make  it  possible  for  the  crystals  to  bend,  and 
explain  their  curved  and  twisted  form. 

That  the  mineral  is  in  the  orthorhombic  sys- 
tem can  easily  be  illustrated  by  the  difference  in 
rapidity  with  which  heat  is  transmitted  in  differ- 
ent directions.  Senarmont's  method  is  to  coat  a 
brachypinacoid  plane  with  wax  and  touch  it  with 
the  point  of  a  hot  wire.  The  wax  is  melted  more 
rapidly  in  the  direction  of  the  c  axis  than  in  the 
direction  of  a.  Consequently  the  resulting  figure 
is  an  ellipse.  Roentgen's  method,  similar  in  prin- 
ciple, is  to  breathe  upon  a  face,  touch  it  with  the 
point  of  a  hot  wire,  then  sprinkle  lycopodium  crystal, 
powder  upon  it.  When  shaken,  the  powder  drops 
from  the  mineral  where  it  was  dry.  The  form  of  the  clean  space  is 
an  ellipse  with  the  long  axis  parallel  to  the  c  axis. 

Stibnite  is  found  with  other  sulphides  (argentite,  galena,  sphalerite, 
cinnabar)  and  with  barite  and  quartz  in  veins  in  granite  and  gneiss. 

The  ancients  used  stibnite  as  a  pigment  to  darken  eyebrows.  Its 
chief  use  at  present  is  as  a  source  of  antimony. 

SUMMARY 

Stibnite. — Sb2S3;  Sb  =  7i.8  per  cent,  8  =  28.2  per  cent.  Ortho- 
rhombic;  (no),  (in),  (113),  (oio).  Massive,  bladed,  fibrous,  granular. 
Cleavage  (oio)  perfect;  glide  planes  (ooi);  slightly  pliable;  fracture 
conchoidal. 

Hardness=2;  gravity  =  4. 6.     Steel  gray;  metallic;  opaque. 

Easily  fusible  (i  in  the  scale) ;  volatilizes;  soluble  in  hydrochloric  acid. 

Japan,  Hungary,  Australia,  California. 


/ 

\j 

I 

p 

, 

i  ^ 

4 

•-~1 

-• 

|no 

010 

i 

i 

i 

i 

FIG.  46. — Stibnite 


48  GUIDE  TO  MINERAL  COLLECTIONS 

Molybdenite 

Molybdenite,  the  sulphide  of  molybdenum  (MoS2),  is  a  soft 
metallic  mineral,  bluish  lead  gray  in  color.  It  occurs  in  six-sided 
(hexagonal)  tabular  crystals  in  quartz  veins  (Plate  VI  b).  In  soft- 
ness, color,  and  form  it  closely  resembles  graphite  but  can  be  distin- 
guished by  the  fact  that  the  color  is  bluish  and  the  mark  left  on  paper 
(the  " streak")  is  bluish,  while  the  color  and  streak  of  graphite  are 
lead  gray.  Molybdenite  (gravity  =  4. 7)  is  also  more  than  twice  as 
heavy  as  graphite. 

Its  crystals  are  often  striated  horizontally,  taper  toward  the  top 
because  of  the  decrease  in  the  diameter  of  its  constituent  lamellae, 
and  show  glide  planes.  Foliated,  scaly,  and  granular  particles  some- 
times are  scattered  through  the  containing  quartz  and  at  other  times 
concentrated  in  the  masses.  With  it  are  often  found  other  sulphides 
such  as  pyrite  and  chalcopyrite.  It  has  been  deposited  from  solution 
in  crystalline  rocks,  such  as  pegmatite  granite,  gneiss,  and  granular 
limestone. 

The  chief  sources  of  supply  in  the  United  States  recently  have 
been  California,  Colorado,  Montana,  Maine,  and  Washington.  None 
is  found  in  Illinois. 

Molybdenum  compounds  are  used  in  coloring  silk,  leather,  and 
porcelain  blue.  They  have  a  limited  use  in  chemical  laboratories  for 
the  determination  of  phosphorus;  in  the  manufacture  of  steel  a  frac- 
tion of  a  per  cent  of  molybdenum  hardens  the  steel  and  changes  its 
coefficient  of  expansion. 

SUMMARY 

Molybdenite. — MoS2;  Mo =60  per  cent,  8  =  40  per  cent.  Hexagonal; 
plates,  scales;  cleavage  parallel  (oooi).  Flexible;  sectile. 

Hardness=i;  gravity  =  4.y.     Bluish  gray;  metallic;  opaque;  greasy. 

Infusible;  soluble  in  nitric  acid. 

California,  Colorado,  Montana,  Washington,  Maine,  Canada,  and 
many  European  localities. 

Galena 

Because  of  its  physical  properties  and  its  importance  commer- 
cially, galena,  the  sulphide  of  lead  (PbS),  is  an  interesting  mineral. 
It  is  found  in  great  masses  or  disseminated  in  limestone,  as  in  the 
Mississippi  Valley  region,  and  in  veins  in  crystalline  rock,  as  in  the 


SULPHIDES 


49 


Cordilleran  region.  In  the  Cordilleras  the  galena  is  usually  argen- 
tiferous and  consequently  one  of  the  chief  sources  of  silver  in  this 
country.  In  the  Mississippi  Valley  region  it  contains  practically  no 
silver  but  is  associated  with  the  zinc  sulphide,  sphalerite. 

Galena  is  mined  in  many  places  in  both  hemispheres,  but  probably 
in  no  place  more  extensively  than  in  Missouri  and  Idaho.  In  early 
days  in  the  Mississippi  Valley  region  the  avocation  of  the  farmers 
was  often  the  quarrying  of  galena  for  lead  from  which  to  cast  bullets 
in  time  of  war  and  for  making  pewter  ware  in  time  of  peace.  Some 
galena  is  found  in  Pope  and  Hardin  counties  in  Illinois  in  connection 


-1 -I- 


FIG.  47. — Cube  truncated  by  octa- 
hedron. 


FIG.  48. — Model  of  a  cube  truncated 
by  an  octahedron. 


with  the  fluorite  mined  there,  and  some  is  produced  in  the  north- 
western portion  of  the  state.  Scattered  crystals  may  be  detected  in 
the  "Niagara"  limestone  at  different  places.  The  finest  samples  shown 
in  the  museum  collection  are  from  Jo  Daviess  County.  No.  421  is  a 
cube  whose  corners  are  truncated  with  octahedron  planes.  It  measures 
over  three  inches  each  way  and  weighs  yf  pounds  (Fig.  49).  No.  3396 
is  another  smaller  cube,  and  No.  267  is  a  large  mass  which  has  been 
incrusted  with  iron  sulphide  (marcasite).  Where  the  incrustation 
has  broken  off,  the  underlying  galena  may  be  seen.  When  one  sees 
this  pronounced  crystallization  he  is  impressed  with  the  fact  that 
when  minerals  have  the  opportunity  they  have  a  form  as  well  defined 
as  that  of  a  flower. 


50  GUIDE  TO  MINERAL  COLLECTIONS 

Galena  is  soft,  heavy,  lead  gray,  metallic,  and  opaque.  It  crys- 
tallizes readily,  so  that  even  massive  forms  when  cleaved  show  the 
structure,  and  well-formed  crystals  are  very  common.  The  usual 
habit  is  fine  cubes  with  the  corners  truncated  by  octahedrons  (Figs. 
47  and  48).  The  octahedrons  may  be  enlarged  so  as  to  almost  dis- 
place the  cube,  or  they  may  become  so  small  as  to  disappear. 

The  cube  faces  are  often  formed  by  very  flat  four-faced  cube 
planes  (hko\  h  and  k  representing  any  two  different  numbers.  If 
h  =  4  and  k  =  i,  the  symbol  is  (410),  a  tetrahedron  often  met  with. 


2  inch 


FIG.  49. — Galena,  Jo  Daviess  County, 
Illinois. 


FIG.  50. — Model  of  planes  appear- 
ing on  galena. 


Crystals  often  exhibit  the  dodecahedron  (no)  in  combination 
with  the  cube  and  octahedron  (Fig.  50). 

Cleavage  is  so  perfect  that  a  single  blow  of  a  hammer  will  shatter 
a  crystal  into  multitudes  of  little  cubes  whose  faces  may  show  stria- 
dons  parallel  to  the  lower  right-hand  trisoctahedron  (441)  due  to 
twining  lamellae  parallel  to  that  plane  (Fig.  51).  Since  glide  planes 
can  be  produced  in  this  direction  by  pressure,  the  striae  may  be  due 
to  that  cause. 

Galena  which  contains  from,  i  to  2  per  cent  of  bismuth  has 
octahedral  cleavage.  When  heated  enough  to  drive  off  the  bismuth, 
the  cleavage  becomes  cubic.  Singularly,  galena  containing  Bismuth 
does  not  decrepitate  when  heated,  as  does  ordinary  galena,  nor  is 


SULPHIDES 


FIG.   51. — Twin   lamellae  in    galena 
parallel  to  (441). 


there  a  change  in  its  specific  gravity.  Further,  with  the  change  in 
crystalline  structure,  there  is  no  decrepitation  such  as  occurs  in  ordi- 
nary galena. 

Galena  usually  contains  small  amounts  of  silver  sulphide,  and  as 
the  amount  present  increases,  the  galena  loses  its  coarse  cubic  struc- 
ture and  becomes  finely  granular. 

When  covered  with  a  layer  of 
wax  and  touched  with  the  point 
of  a  hot  wire,  the  wax  melts  in 
a  circle,  showing  that  galena  is 
in  the  regular  system. 

Argentite,  sphalerite,  chalco- 
pyrite,  pyrite,  fluorite,  quartz, 
calcite,  and  rhodochrosite  accom- 
pany galena  in  limestones  or  in 
crystalline  rocks. 

Since  galena  furnishes  the 
lead  of  the  world,  it  is  one  of  the 
most  useful  of  minerals. 

Lead  is  used  in  plumbing,  in  the  manufacturing  of  paint,  medicine, 
alloys,  shot,  etc. 

SUMMARY 

Galena. — PbS;  Pb  =  86.6  per  cent,  8  =  13.4  per  cent.  Regular; 
holosymmetric ;  (100),  (in),  (no),  (221).  Cleavage  (100)  perfect; 
fracture  even;  nearly  sectile. 

Hardness  =  2.5;  gravity  =  7 .  5.     Lead  gray;  metallic;  opaque. 

Easily  fusible,  decrepitates;  soluble  in  nitric  acid. 

Mississippi  Valley,  Cordilleran  region. 

Argentite 

Argentite,  the  sulphide  of  silver  (Ag2S),  is  one  of  the  chief  sources 
of  the  metal.  It  closely  resembles  galena  but  does  not  occur  in  such 
distinct  crystals.  Usually  it  is  in  the  form  of  dendritic,  scaly,  earthy, 
or  granular  masses.  It  does  not  cleave  as  readily  as  galena  but  is 
sectile.  It  is  associated  with  the  same  minerals  and  is  found  in  crys- 
talline rocks  such  as  are  wont  to  contain  gold,  silver,  and  other 
precious  minerals.  The  best  crystal  shown,  No.  3822,  was  obtained 
at  Guanajuato,  Mexico. 


52  GUIDE  TO  MINERAL  COLLECTIONS 

SUMMARY 

Argentite. — Ag2S;  Ag=87.i  per  cent,  8=12.9  per  cent.  Regular, 
holosymmetric;  (100),  (no).  Cleaves  imperfectly  parallel  (100),  (no); 
sectile;  fracture  sub-conchoidal. 

Hardness  =  2 .  5 ;  gravity  =  7.3.  Color  and  streak  lead  gray;  metallic; 
opaque. 

Melts  readily;  soluble  in  nitric  acid. 

In  the  mountain  ranges  in  western  North  and  South  America,  and  in 
many  European  and  Australian  localities. 

Chalcocite 

In  Arizona  during  1918  nearly  as  much  copper  was  produced  as 
was  obtained  from  Michigan,  Montana,  and  Utah  combined.  The 
ore  consists  chiefly  of  chalcocite  (Cu2S),  a  mineral  which  is  dark 
lead  gray  in  color,  metallic,  and  opaque,  and  occurs  in  granular  or 
compact  masses.  It  resembles  argentite  in  general  appearance,  but 
is  more  brittle  and  is  often  tarnished  blue  or  green  when  the  addition 
of  sulphur  changes  the  chalcocite  (Cu2S)  to  covellite  (CuS),  or  the 
addition  of  iron  changes  it  into  erubescite  (Cu3FeS3) .  •  While  chal- 
cocite crystallizes  in  the  orthorhombic  system,  well-formed  crystals 
are  rare.  Since  the  angle  between  the  prism  planes  (no)  is  60°, 
chalcocite  often  looks  as  if  it  were  a  hexagonal  mineral.  When 
several  crystals  are  twinned  about  the  prism  planes,  the  form  is  even 
more  deceptive. 

Chalcocite  is  found  in  connection  with  other  sulphides  at  many 
localities  in  the  Cordilleran  range.  No  example  has  been  reported  in 

Illinois. 

SUMMARY 

Chalcocite. — Cu2S ;  Cu  =  79 . 8  per  cent,  S  =  20 . 2  per  cent.  Orthorhom- 
bic; a:&:c=o.58:i:o.97.  Common  planes  (no),  (ooi),  (023),  (113); 
twinned  on  (no),  (032);  cleavage  imperfect  (no);  sectile;  fracture 
conchoidal. 

Hardness  =2. 5;  gravity  =5. 7.  Lead  gray;  streak  black;  metallic;, 
opaque. 

Easily  fusible;  soluble  in  nitric  acid. 

Cordilleran  region,  England,  Germany. 

Sphalerite 

Many  localities  in  which  lead  is  abundant  are  also  famous  because 
of  their  great  deposits  of  sphalerite  (ZnS).  The  early  German  miners 
who  were  seeking  lead  were  disappointed  when  they  found  sphalerite 


SULPHIDES  53 

instead,  and  therefore  called  it  Blende  from  blenden,  "to  deceive." 
"Sphalerite,"  from  the  Greek,  has  the  same  meaning. 

Pure  sphalerite  has  the  color  of  resin.  See  the  specimen  from 
Spain  (No.  3765).  Usually  it  is  dark  because  of  impurities  like  iron, 
cadmium,  manganese,  tin,  thallium,  indium,  and  gallium  that  are 
often  present  in  varying  quantities.  Some  sphalerite  contains  as 
much  as  20  per  cent  of  iron.  Miners  call  the  dark  varieties  "Black 
Jack."  See  specimens  from  Colorado,  Kansas,  and  Missouri.  Gal- 
lium and  indium  were  first  discovered  in  sphalerite.  Sphalerite 
occurs,  as  do  most  of  the  other  sulphides,  when  igneous  rocks  such  as 
granites,  diabases,  and  porphyries  are  in  contact  with  metamorphic 
rocks  such  as  gneisses,  schists,  and 
granular  limestones,  especially  where 
these  rocks  have  been  fissured  and  sub- 
sequently cemented  by  vein-forming 
materials.  In  the  Mississippi  Valley 
region,  however,  sphalerite  usually  is 
found  in  beds  or  is  scattered  through 
the  limestone. 

Well-crystallized    specimens    are 
seen  to  follow  the  laws  of  the  regular  FIG.  52.— Sphalerite 

system   and    to   illustrate   the   same 

class  of  symmetry  as  that  which  is  shown  by   the   diamond,  the 
"  tetrahedrite  class." 

Common  forms  such  as  that  in  Figure  52  are  combinations  of 
tetrahedrons  (in),  dodecahedrons  (no),  and  trapezohedrons  (311). 
The  tetrahedrons  are  positive  and  negative,  and  upon  the  alternate 
octants  only  occur  the  planes  which  together  would  produce  the 
hemihedral  form  called  the  three-faced  tetrahedron  (311)  (Figs.  53 
and  54).  Supplementary  tetrahedrons  combined  with  cubes  are 
characteristic  (Fig.  55).  The  positive  and  negative  tetrahedrons 
may  be  distinguished  by  the  difference  in  their  size,  by  their  differing 
smoothness,  by  the  different  markings  which  their  faces  show  when 
they  are  etched  with  dilute  hydrochloric  acid,  and  by  a  pyro-electric 
test.  To  make  this  test  cut  a  plate  parallel  to  a  face  of  each  of  the 
two  tetrahedrons  in  turn.  Insulate,  connect  with  an  electroscope, 
and  touch  with  the  point  of  a  heated  wire.  One  tetrahedron  will 
become  positively  electrified,  and  the  other  negatively. 


54 


GUIDE  TO  MINERAL  COLLECTIONS 


Twin  lamellae  parallel  to  tetrahedral  faces  are  common  in  the 
sphalerite  of  many  localities. 

Stibnite,  galena,  afgentite,  pyrite,  marcasite,  chalcopyrite,  fluorite, 
quartz,  calcite,  and  barite  are  the  associates  of  sphalerite. 


FIG.   53. — Model   of  a   three-faced 
tetrahedron,  a  tristetrahedron. 


FIG.    54. — Construction    of    trigonal 
tristetrahedron. 


FIG.  55. — Sphalerite 


The  region  around  Joplin,  Missouri ,. 
has  produced  probably  more  sphalerite 
than  has  any  other  locality  in  the  world, 
and  Illinois  is  the  leading  state  in  zinc 
smelting  from  these  ores.  The  museum 
collection  contains  also  specimens  from 
Alston  Moor,  England,  and  Kapnik, 
Hungary,  two  places  famous  for  their 
many  fine  crystals. 

Sphalerite  is  the  most  important 
source  of  zinc,  and  the  metal  obtained 

from  it  is  used  in  galvanizing  iron,  in  zinc  plating,  in  paint  manu- 
facture, and  in  medicine.      •  • 

SUMMARY 

Sphalerite. — ZnS;  Zn  =  6;  per  cent,  8  =  35  per  cent.  Regular,  tetra- 
hedrite  class;  (in),  (no),  (311),  (100).  Cleavage  perfect  parallel  (no);, 
brittle;  fracture  conchoidal. 

Hardness =3. 5;  gravity =4.  Yellow,  adamantine,  translucent;  refrac- 
tion 7^=2.37. 

Fusible  with  difficulty;  soluble  in  hydrochloric  acid. 

Kansas,  Missouri,  Illinois,  Wisconsin,  Colorado,  Utah,  Montana, Europe. 


SULPHIDES  55 

Cinnabar 

Though  mercury  occurs  sometimes  uncombined  in  nature,  the 
chief  source  of  the  metal  is  cinnabar  (HgS).  Cinnabar,  a  word  used 
in  India  two  thousand  years  ago,  means  "red  resin"  and  is  well 
applied,  since  the  color  of  the  mineral  is  bright  red  and  the  streak 
vermilion.  See  specimens  No.  3401  and  No.  3893.  Impurities 
make  it  brown  or  slaty  (No.  593).  Crystals  of  cinnabar  are  rare. 
The  mineral  is  notable  for  its  refractive  power,  the  ordinary  ray  (o>) 
being  more  strongly  refracted  than  it  is  in  diamond.  co  =  2  .85. 

Further,  a  ray  of  light  entering  the  crystal  in  almost  any  direction 
is  divided  into  two  rays  which  vibrate  at  right  angles  to  each  other. 
That  is,  .it  is  "  doubly  refracted."  One  ray  is  called  the  ordinary  (co) 
and  the  other  the  extraordinary  (e).  When  the  difference  between 
them  is  great,  the  double  refraction  or  "birefringence"  is  said  to  be 
strong.  In  cinnabar  e — co  =  o .  3  5 . 

Of  late  years  more  cinnabar  has  been  produced  in  the  United 
States  than  in  any  other  country,  and  of  this  production  the  greater 
part  is  furnished  by  California.  None  is  found  in  Illinois. 

SUMMARY 

Cinnabar. — HgS;  Hg=86.2  per  cent,  8=13.8  per  cent.  Hexagonal; 
"quartz  class":  (1010),  (oooi),  rhombohedrons  (ion);  c=  1.145.  Cleav- 
age good,  parallel  (1010);  fracture  uneven. 

Hardness  =2. 5;  gravity =8. 2.  Cochineal  red;  streak  vermilion; 
luster,  metallic,  adamantine;  translucent.  Refraction  very  strong, 
(0=2.85;  birefringence,  positive,  very  strong  (€—(0  =  0.35).  Circular 
polarization  very  strong. 

Volatile;  soluble  in  nitric  acid. 

New  Almaden,  California;  Spain;  and  south  Russia. 

Pyrrhotite 

Pyrrhotite  (-jrvppos,  "reddish")  is  a  bronze-colored,  magnetic 
iron  sulphide,  which  occurs  in  massive  forms  and  is  often  lamellar  in 
structure. 

Its  crystallization  is  so  imperfect  as  to  leave  doubt  concerning  its 
true  nature,  and,  being  opaque,  its  optical  properties  can  shed  no 
light  on  the  question.  However,  its  structure  is  probably  such  as 
characterizes  the  hexagonal  system. 


56  GUIDE  TO  MINERAL  COLLECTIONS 

There  is  also  doubt  as  to  the  chemical  composition  of  pyrrhotite. 
Different  formulae  have  been  given  to  it,  ranging  from  Fe6S7  to 
FenSI2.  The  formulae  all  agree  closely  with  the  monosulphide  FeS, 
troilite,  which  is  a  mineral  not  known  on  the  earth  but  common  in 
some  meteorites. 

Pyrrhotite  is  not  so  abundant  as  other  iron  sulphides.  The  iron 
which  it  contains  cannot  be  separated  from  the  sulphur  without 
great  difficulty.  However,  in  some  localities,  as  at  Duck  town,  Ten- 
nessee, immense  quantities  of  sulphuric  acid  are  made  from  it.  Nickel 
and  cobalt  are  often  present  in  paying  quantities,  and  the  nickelifer- 
ous  pyrrhotite  of  Pennsylvania,  Canada,  and  Norway  is  an  important 
source  of  those  metals. 

SUMMARY 

Pyrrhotite. — FenSi2;  Fe  =  56  to  61  per  cent;  8  =  44  to  39  per  cent. 
Hexagonal  plates,  masses.  Brittle;  fracture  uneven. 

Hardness  =  4;  gravity  =  4. 6.  Bronze  yellow;  streak  grayish  black; 
metallic;  opaque;  magnetic. 

Fusible;  soluble  in  nitric  acid. 

Appalachian  and  Cordilleran  systems;  Europe. 

Erubescite 

Erubescite,  the  "blushing  ore"  (Cu3FeS3),  owes  its  beauty  to  the 
ease  with  which  it  tarnishes.  It  is  called  also  bornite,  variegated 
copper,  horseflesh  ore,  peacock  ore.  When  freshly  broken  it  has  a 
coppery  or  bronzy  color,  but  soon  tarnishes  to  a  vivid  blue  or  purple. 
Its  color  is  its  most  interesting  characteristic. 

Granular  or  compact  masses  are  the  most  usual,  but  sometimes 
crystals  in  cubes  can  be  distinguished.  As  is  always  the  case,  the 
crystals  represent  the  purest  condition. 

Cornwall,  England,  South  Africa,  and  some  of  the  Cordilleran 
states  furnish  the  best  crystals  and  the  most  abundant  supply  of 
erubescite.  Our  best  samples  were  obtained  in  Colorado  (No.  3753) 
andJNew  Mexico  (No.  2195). 

SUMMARY 

Erubescite. — Cu3FeS3;  Cu=55. 5  per  cent,  Fe=  16.4  per  cent,  8  =  28.  i 
percent.  Regular;  (100);  twinned  on  (in);  cleavage  imperfect,  parallel 
(in);  slightly  sectile;  fracture  sub-conchoidal. 


SULPHIDES 


57 


Hardness=3;   gravity  =5.    Pinchbeck  brown,  bronze,  tarnished  blue; 
streak  grayish  black;  metallic;  opaque. 
Fusible;  soluble  in  nitric  acid. 
With  other  copper  ores  in  Colorado,  Montana,  South  Africa. 

Chalcopyrite 

Very  closely  related  to  erubescite  in  chemical  composition  but 
much  more  pronounced  in  physical  characteristics  and  commercial 
importance  is  chalcopyrite  (CuFeS2),  i.e.,  copper  pyrite,  a  name  given 
by  Henckel  in  1725  when  a  difference  between  this  and  pyrite  was 


FIG.  56. — Acute  primary  bipyramid 


FIG.  57. — Obtuse  primary  bipyramid 


for  the  first  time  noticed.  Chalcopyrite  and  chalcocite  are  the  chief 
sources  of  copper  today. 

Lustrous,  clean-cut  crystals  of  chalcopyrite  are  common,  and  were 
early  studied  by  crystallographers  who  thought  they  were  in  the 
regular  system  until,  in  1822,  accurate  measurements  showed  that 
the  c  axis  is  0.985  when  a  and  b  are  unity.  Hence  the  crystals  are 
in  the  Tetragonal  System,  that  system  in  which  the  c  axis  is  longer  or 
shorter  than  the  a  and  b,  the  a  and  b  axes  are  equal,  and  all  three  axes 
are  at  right  angles.  The  symbol  (i 1 1)  indicates  a  bipyramid  which  is 
acute  when  the  c  axis  is  longer  than  the  lateral  axes  (Fig.  56),  or  obtuse 
when  the  c  axis  is  shorter  than  the  others  (Fig.  57). 

Since  the  lateral  axes  are  equal  and  interchangeable,  a  form  whose 
symbol  is  (101)  will  be  a  secondary  bipyramid,  instead  of  one  con- 
sisting of  dome  planes,  as  in  the  orthorhombic  system  (Fig.  58). 


GUIDE  TO  MINERAL  COLLECTIONS 


Symbols  such  as  (211)  or  (331),  etc.,  indicate  the  ditetragonal 
bipyramid  (Figs.  59  and  60),  since  the  two  or  three  can  be  applied  to 
each  lateral  axis  in  turn,  thus  indicating  two  planes  in  each  octant. 

Similarly  there  are  three  prisms:  a  pri- 
mary, (no)  (Fig.  61);  a  secondary  turned  45° 
to  it,  (100)  (Fig.  62);  and  a  ditetragonal 
prism,  (210)  (Fig.  63).  These  with  the  basal 
plane  represent  the  simple  holohedral  forms 
of  the  system.  Figure  64  shows  a  combination 
of  several  of  these  planes. 

Hemihedral  forms  are  constructed  on  the 
same  plan  as  were  those  in  the  systems  here- 
tofore described.  For  example,  when  the 
alternate  pyramid  faces  only  are  developed, 
a  bisphenoid  results  (Fig.  65).  It  may 


FIG.  58.— Model  of  a 
secondary  bipyramid. 


FiG/5Q. — Ditetragonal  bipyramid 


FIG.   60. — Model  of  a   ditetragonal 
bipyramid. 


be  either  positive  or  negative.  If  the  planes  in  alternate  octants 
of  a  ditetragonal  pyramid  are  developed,  the  tetragonal  scaleno- 
hedron  is  produced.  Tetragonal  scalenohedrons  possess  two  planes 


SULPHIDES 


59 


of    symmetry   intersecting    at   right    angles   in    the  c  axis,    which 
is  an  axis  of  alternating  symmetry.     They  are  so  well  represented 


a* 


1      I 


l 


FIG.  61. — Primary  prism 


FIG.  62. — Secondary  prism 


FIG.  63. — Model  of  a  ditetragonal 
prism. 


FIG.  64. — Combination  of  primary 
prism  (no),  secondary  prism  (100), 
secondary  bipyramid  (101),  and  ditet- 
ragonal bipyramid  (211). 


in  chalcopyrite  that   the  class  has  been  called  the  "  chalcopyrite 
class  of  symmetry." 

Figure  66  represents  the  most  usual  chalcopyrite  crystal.     It  is 
composed  of  the  positive  scalenohedron.     Pyramid  planes  with  the 


6o 


GUIDE  TO  MINERAL  COLLECTIONS 


symbol  (201)  often  appear  on  the  edges.     The  scalenohedrons  may 
be  either  acute  or  obtuse. 

Figure  67  represents  a  form  composed  of  the  prism  (no),  scaleno- 
hedrons (in)  and  (101),  and  the  basal  plane  (ooi). 

Two  kinds  of  twins  are  common.     In  one  the  twinning  plane  is 

(in)  and  produces  a  form  so  similar 
to  the  twin  characteristic  of  the 
mineral  spinel  as  to  be  called  the 
" spinel  twin."  (The  "spinel  twin" 
proper  is  a  form  in  the  regular 
system.) 

The  faces  of  one  of  the  scaleno- 
hedrons are  bright,  while  those  of  the 
other  are  dull. 

In  the  second  form  of  twinning, 
a  central  crystal  (201)  is  surrounded 
by  four  other  crystals  which  are  joined 
on  the  primary  pyramid  plane  (in), 


FIG.  65. — Model  of  a  bisphenoid 


021 


110 


11O 


FIG.  66. — Chalcopyrite 


FIG.  67. — Chalcopyrite,  French  Creek, 
Pennsylvania. 


forming  a  composite  twin  (Fig.  68).  As  is  generally  the  case  with 
all  minerals,  massive  forms  are  the  rule  and  evident  crystals  the 
exception. 

The  color  of  chalcopyrite  is  bronze  yellow  and  its  streak  is  greenish 
black.     Because  of  surface  alterations  it  readily  tarnishes,  and  takes 


PLATE  VII 


a,  Group  of  pyrite  cubes,  showing  stria- 
tions,  Central  Cityj  Colorado. 


b,  Pyrite.     A  pyritohedron  and  cubes,  Colorado 


SULPHIDES  6 1 

on  beautiful  iridescent  colors.     The  vivid  blue  is  due  to  the  forma- 
tion of  covellite  (CuS). 

The  Cordilleran  region  from  Arizona  to  Montana  furnishes  large 
quantities  of  chalcopyrite.     Many  fine  crystals  have  been  found  at 
French    Creek,    Pennsylvania,    the    Hartz 
Mountains,  and  Cornwall, 

SUMMARY 

Chalcopyrite. — CuFeS2;  01  =  34.  5  per  cent, 
Fe  =  30.5  per  cent,  8  =  35  per  cent.  Tet- 
ragonal; symmetry  ditetragonal  alternating 
(chalcopyrite  class);  a: c=  1:0.985.  Common 
forms  (in),  (101),  (211),  (ooi),  (201),  (114,) 
(441) ;  twinned  about  normal  of  (in).  Brittle; 
fracture  conchoidal.  FlG.  68.— Chalcopyrite, 

Hardness  =  4;  gravity  =  4.  2.    Brass  yellow,        Neudorf.     Twinned  paral- 
tarnishes  blue;  streak  greenish  black;  metallic;       lei  to  (in), 
opaque. 

Fusible;  soluble  in  nitric  acid. 

Western  United  States,  Pennsylvania,  Harz,  Cornwall. 

Pyrite 

This  iron  sulphide  is  more  abundant  than  any  mineral  thus  far 
considered.  It  is  found  in  all  kinds  of  rocks,  with  all  kinds  of  mineral 
associates,  and  in  all  parts  of  the  world.  In  Illinois  it  occurs  in  the 
underlying  rocks — the  shale,  limestone,  and  sandstone,  and  in  the 
sand  and  gravel  carried  in  by  Pleistocene  glaciers. 

The  name  pyrite  (irvp,  Greek  "fire")  was  used  by  Dioscorides 
and  Pliny  in  the  first  century  after  Christ  for  minerals  which  gave 
sparks  when  struck  by  the  hammer,  and  was  applied  not  only  to 
minerals  in  which  the  sparks  are  due  to  the  combustion  of  the  mineral 
itself  but  to  hard  minerals  like  flint  in  which  the  sparks  are  due  to 
glowing  particles  intensely  heated  by  the  friction. 

Pyrite  differs  from  the  iron  sulphide  already  considered,  pyrrho- 
tite,  in  being  neither  magnetic  nor  bronze  colored,  and  from  the 
copper  iron  sulphide,  chalcopyrite,  in  being  brass  yellow  and  not  deep 
yellow  as  in  chalcopyrite. 

It  occurs  as  masses,  large  and  small  crystals,  and  minute  yellow 
specks  in  sedimentary,  igneous,  and  metamorphic  rocks. 


62 


GUIDE  TO  MINERAL  COLLECTIONS 


Two  forms  of  crystals  are  common  and  several  others  abundant. 
One  of  the  most  typical  is  that  which  has  the  outline  of  a  cube  (100) 
(Plate  Vila),  but  whose  true  symmetry  is  indicated  by  the  striations 
on  each  face.  These  striations  show  that  the  cube  is  built  up  by 
repetition  of  many  planes  of  a  form  which  is  so  characteristic  of 
pyrite  as  to  have  been  named  the  "  pyritohedron "  (pentagonal 
dodecahedron)  (Plate  VII  b).  The  pyritohedron  is  formed  when 
the  alternate-  quarters  of  the  four-faced  cube  (the  inner  part  of 


FIG.  69. — Pyritohedron  derived 
by  disappearance  of  tetrahexahe- 
dral  planes  darkened,  and  growth 
of  the  other  planes. 


FIG.  70. — Model  of  a  diploid 


Fig.  69)  are  developed,  beginning  with  the  plane  (210).  The  black 
strips  with  which  the  glass  faces  of  the  outer  figure  are  bound  mark 
the  pyritohedron.  Clear-cut  pyritohedrons  are  so  common  that 
every  collector  can  obtain  them.  Occasionally  a  form  shown  in 
Figure  70,  called  a  diploid,  is  found.  It  results  when  the  plane 
(321)  and  each  alternate  plane  in  the  right-hand  octant  of  the  hexocta- 
hedron  and  the  planes  of  the  like  symbol  in  the  other  octants  are 
developed  to  the  exclusion  of  their  neighbors. 

Both  the  diploid  and  the  pyritohedron  agree  in  this,  that  if 
revolved  around  any  one  of  the  four  octahedral  axes,  i.e.,  the  lines 
extending  through  the  center  of  the  crystal  and  perpendicular  to  an 
octahedral  plane  (Fig.  23),  each  of  its  faces  would  be  in  the  position 
previously  occupied  by  the  adjoining  face  three  times  during  a  com- 
plete revolution.  The  faces  are  said  therefore  to  have  four  trigonal 


SULPHIDES 


axes.  If  revolved  around  the  crystallographic  axes  (#,  b,  c)  the  planes 
are  in  similar  positions  twice  during  a  complete  revolution  and  hence 
these  axes  are  called  digonal  axes.  Since  planes  through  any  two  of 
these  digonal  axes  (a  and  c,  or  b  and  c,  or  a  and  b)  are  planes  of  sym- 
metry, the  digonal  axes  are  called  didigonal  axes.  Pyrite  crystals 
have  three  didigonal  axes.  Their  faces  are  in  pairs  about  a  center. 
Hence  the  pyrite  class  of  the  regular  system  has  a  center,  three  planes, 
three  didigonal  and  four  trig- 
onal axes  of  symmetry.  This 
symmetry  is  called  tesseral 
central  symmetry. 

Cube,  octahedron,  pyrito- 
hedron,  and  diploid  appear  in 
various  combinations.  The 
edges  of  the  pyritohedron 
(210)  are  truncated  by  the 
cube  (100)  (Fig.  71). 

Etching  with  aqua  regia 
produces  figures  symmetri- 
cally arranged  in  respect  to 
the  cube  planes. 

Sulphides   of   nickel    and  FIG.   71.— Model   of  a   combination   of 

cobalt  are  often  found  in  py-       pyritohedron  (210)  and  cube  (100). 
rite    as    isomorphous    inter- 
mixtures, i.e.,  mixtures  of  substances  having  the  same  crystalline  form. 
Chalcopyrite,  marcasite,   and  silver  sulphide  are  often   associated 
with  it. 

The  most  important  impurity,  however,  is  gold,  which  is  often 
present  as  a  metal  scattered  through  the  pyrite  in  invisible  particles. 
Much  of  the  gold  of  the  world  is  now  obtained  by  crushing,  roasting,, 
smelting,  and  cyaniding  pyrites,  and  much  of  the  placer  gold  may 
have  originally  come  from  the  same  source. 

The  chief  use  of  pyrite  is  in  the  manufacture  of  sulphuric  acid, 
sulphur,  and  iron  oxide  to  be  employed  as  polishing  powder  and 
paint.  Iron  for  steel  manufacture  cannot  be  obtained  from  it, 
since  thorough  separation  of  the  sulphur  is  almost  impossible  and 
a  fraction  of  i  per  cent  remaining  in  the  iron  renders  it  brittle 
while  hot. 


GUIDE  TO  MINERAL  COLLECTIONS 


SUMMARY 

Pyrite. — FeS2;  Fe  =  46.6  per  cent,  8  =  53.4  per  cent.  Regular; 
pyrite  class:  (100),  (in),  (210),  (321),  (421).  Supplementary  twins; 
granular;  massive;  brittle;  fracture  conchoidal. 

Hardness  =  6;  gravity  =5.1.  Pale  brass  yellow;  streak  greenish 
black;  metallic;  opaque. 

Burns  on  charcoal  and  gives  off  SO2;  fuses  to  magnetic  globules; 
soluble  in  nitric  acid. 

Ubiquitous. 

Marcasite 

The  same  chemical  composition  is  ascribed  to  marcasite  as  to 
pyrite,  namely,  FeS2.  But  there  are  pronounced  physical  differences. 
Marcasite  crystallizes  in  the  orthorhombic  system  and  in  the  holo- 
symmetric  class.  The  crystals  have  a  center  of  symmetry;  three 
planes  of  symmetry  intersecting  at  right  angles  in  the  crystallo- 
graphic  axes;  and  the  c  axis  is  a  didigonal  axis  of  symmetry,  that  is, 
if  revolved  around  the  c  axis  the  planes 

assume  similar  positions  twice  in  one  w—T^^OlS 

complete   revolution,   making   the   c  //  /*   >/~Voi2. 

axis  a  digonal  axis.  Since  planes  of 
symmetry  intersect  in  this  axis,  it  is 
called  a  didigonal  axis.  A  form  j 

i 


n 


Oil 


FIG.  72. — Marcasite 


FIG.  73. — Marcasite 


common  to  marcasite  is  composed  of  the  prism  (no),  base  (ooi), 
and  brachydomes  (on)  and  (013)  (Fig.  72).  Prisms  of  marcasite 
are  usually  terminated  by  various  brachydome  planes  (Fig.  73). 
Isolated  crystals  are  rare.  Because  of  multiple  twinning  they  gener- 
ally show  jagged  outlines  and  re-entrant  angles.  Before  marcasite 
was  distinguished  from  pyrite,  these  forms  were  called  "spearhead 
pyrites,"  " cockscomb  pyrites,"  " radiated  pyrites,"  "hepatic  pyrites," 


PLATE  VIII 


Marcasite,  Jo  Daviess  County,  Illinois 


PLATE  IX 


Marcasite  disks,  Gulf  Mine,  Sparta,  Randolph  County,  Illinois 


SULPHIDES  65 

etc.  Four  or  five  individuals  consisting  of  various  dome  and  basal 
planes  twinned  parallel  to  the  prism  produce  the  "spear-head  pyrites" 
(Fig.  74).  "Cockscomb  pyrites"  result  from  repeated  twinning  par- 
allel (no)  so  as  to  produce  individuals  parallel  to  each  other  (Fig.  75). 
The  prisms  are  short  and  the  striated  basal  plane  long.  Radi- 
ated, nodular,  and  stalactitic  forms  are  abundant  (Plate  VIII). 
More  marcasite  than  pyrite  is  found  in  Illinois.  No.  3287  from 
Sparta  shows  disks  which  are  not  surpassed  in  abundance  and  perfec- 
tion by  any  locality  (Plate  IX). 

Plate  X  shows  a  portion  of  a  large  radiated  mass  and  Plate  XI 
a  coating  of  marcasite  on  cubes  of  galena  which  are  resting  upon  a. 


-no 


L10 


FIG.  74. — "Spearhead  pyrites" 


FIG.  75. — "  Cockscomb  pyrites " 


botryoidal  mass  of  sphalerite,  well  illustrating  the  association  of  the 
sulphides. 

Haidinger  (1845),  recognizing  the  orthorhombic  form  of  mar- 
casite, reserved  Pliny's  term  pyrite  for  the  regular  form  and  applied 
the  old  Moorish  word  "marcasite"  to  the  orthorhombic.  It  is  a. 
common  error  to  use  the  name  pyrite  when  marcasite  is  meant. 
Marcasite  is  orthorhombic,  white  in  color  and  streak,  not  as  heavy 
and  more  easily  decomposed  than  pyrite.  Even  in  museum  cases  it 
disintegrates  and  becomes  covered  with  white  efflorescent  iron  sul- 
phate (melanterite)  and  forms  sulphuric  acid  which  attacks  the 
material  upon  which  it  rests.  Its  instability  may  be  due  to  minute 
spicules  of  troilite  (FeS),  a  mineral  heretofore  identified  in  meteorites 
only. 

When  marcasite  is  heated  to  200°  C.  in  a  sealed  tube  with  a 
copper  sulphate  solution,  it  yields  a  solution  entirely  ferrous.  Pyrite 


66  GUIDE  TO  MINERAL  COLLECTIONS 

treated  in  the  same  way  yields  a  solution  19.9  per  cent  ferrous  and 

II 
80 .  i  per  cent  ferric.     Hence  the  formula  of  marcasite  is  FeS2  while 

III  II 

that  of  pyrite  is  4FeS2  and  FeS2. 

Since  marcasite  is  most  common  in  limestones  and  shales,  and 
pyrite  in  crystalline  rocks,  their  physical  differences  are  doubtless  due 
to  their  origin — marcasite  having  been  hastily  deposited  from  cold 
solutions,  and  pyrites  slowly  deposited  from  hot  solutions,  pyrite  rep- 
resenting the  more  successful  molecular  grouping  and  showing  that 
metamorphism  produces  in  the  lower  zones  of  the  earth's  crust  min- 
erals of  more  complete  symmetry,  higher  specific  gravity,  and  greater 
hardness  than  those  found  in  the  upper  zones. 

Marcasite  has  been  made  in  the  laboratory  from  an  acid  solution 
and  with  temperatures  not  above  300°  C.  When  the  solution  was 
neutral,  pyrite  crystals  were  formed.  The  most  favorable  conditions 
were  found  to  be  an  acidity  amounting  to  about  i .  2  per  cent  free 
sulphuric  acid  and  a  temperature  of  100°.  At  450°  marcasite  changes 
to  pyrite. 

Both  marcasite  and  pyrite  are  common  fossilizing  material 
because  of  the  reducing  action  which  decaying  organisms  exert  upon 
iron  sulphate  solutions.  Marcasite  decomposing  in  moist  air  forms 
sulphuric  acid,  which  can  change  the  limestones  surrounding  it  to 
gypsum: 

SUMMARY 

Marcasite. — FeS2;  Fe  =  46.6  per  cent,  $-=53.4  per  cent.  Ortho- 
rhombic;  holosymmetric;  a:b:c  =  o.  766:  i:  i.  234;  forms  (no),  (ooi),  (on), 
(018);  twinned  on  (no).  Crystals  grouped,  nodular,  stalactitic,  radiated, 
massive.  Cleavage  imperfect  (lu);  brittle;  fracture  uneven. 

Hardness  =  6;  gravity  =  4. 8.  Pale  brass  yellow;  streak  greenish  gray; 
metallic;  opaque. 

Soluble  in  nitric  acid.     Fuses  readily. 

Ubiquitous. 

Arsenopyrite 

Arsenopyrite  resembles  marcasite  in  its  crystallography  (Figs.  76 
and  77)  but  is  whiter,  has  a  black  streak,  and  is  softer  and  heavier. 
It  often  contains  as  high  as  9  per  cent  of  cobalt  in  the  form  of  an 
isomorphous  intermixture  of  the  cobalt  sulphide,  glaucodot.  Arseno- 


PLATE  X 


Marcasite,  showing  radiated  internal  structure 


PLATE  XI 


Marcasite  coating  galena,  Marsden  Mine,  Jo  Daviess  County,  Illinois 


SULPHIDES 


67 


pyrite  is  the  chief  source  of  arsenic,  a  metal  used  principally  in  the 
manufacture  of  Paris  green,  in  various  medicinal  compounds  and 
embalming  fluids,  and  in  glass  and  enamel  manufacture. 


FIG.  76. — Arsenopyrite 


FIG.  77. — Arsenopyrite 


SUMMARY 

A  rsenopyrite. — FeAsS ;  Fe  =  34 . 3  per  cent,  As  =  46 .  o  per  cent,  8  =  19.7 
per  cent.  Orthorhombic ;  holosymmetric;  a:b:c  =  o. 677:1:1. 08;  (no), 
(on),  (014);  twinned  on  (101);  massive;  cleavage  fair  (no);  brittle; 
fracture  uneven. 

Hardness  =5.5-,  gravity  =  6.     Silver  white ;   streak  grayish  black. 

Soluble  in  nitric  acid. 

Freiberg,  Cornwall,  Ontario,  Washington. 


CLASS  III.    SULPHANTIMONITES,  SULPHARSENITES 
PYRARGYRITE  GROUP 

Pyrargyrite,  a  silver  sulphantimonite,  and  proustite,  a  silver  sul- 
pharsenite,  called  the  "ruby  silver  ores"  because  of  their  wine-red 
color  when  fresh,  are  excellent  examples  of  isomorphism,  since  they 
crystallize  in  forms  very  similar  and  with  angles  nearly  identical, 
though  one  contains  antimony  and  the  other  arsenic.  Their  structure 
places  them  in  the  hexagonal  system,  and  their  symmetry  is  said  to 
be  "di trigonal  polar"  (tourmaline  class).  It  is  polar,  inasmuch  as 
the  crystals  are  different  at  different  ends.  If  the  difference  is  not 
shown  by  developed  planes,  it  may  nevertheless  be  disclosed  by  the 


-c 


FIG.  78. — Symmetry  planes  of  a  di- 
trigonal  polar  crystal. 


FIG.  79. — Axes  of  hexagonal  system 


stria tions  on  the  prism  planes,  since  the  striations  are  not  symmetrical 
toward  both  ends.  The  symmetry  is  ditrigonal,  since  three  planes  of 
symmetry  intersect  in  the  c  axis,  and  if  the  forms  are  revolved  around 
this  axis  the  planes  are  in  a  similar  position  three  times  in  one  com- 
plete revolution  (Fig.  78). 

In  the  hexagonal  system  are  grouped  those  crystals  which  have 
three  lateral  axes  of  equal  length  intersecting  each  other  at  60°,  and 
perpendicular  to  them  a  vertical  axis  longer  or  shorter  than  they  are. 
The  method  of  naming  the  axes  can  be  understood  from  Figure  79. 
The  holosymmetric  (holohedral)  forms  are  three  pyramids  and  three 

68 


SULPHANTIMONITES,  SULPHARSENITES 


69 


prisms,  and  the  ratios  are  always  given  thus :  a-.bia^.c.    The  sum  of  the 
intercepts  on  the  first  three  is  always  zero.     If  (hkU)  represents  any 


FIG.  80. — Model  of  a  primary  pyramid 

symbol,  then  h-\-k-\-i=o.  The  pri- 
mary pyramid  (Fig.  80)  is  a  form 
whose  parameter  is  i :  oo  :  i :  i  and 
whose  symbol  is  (1011). 


Parameter 

1:00  :i:i 


Ratio 

a  b  di  c 
1*0" i  "i 


Symbol 
(lOll) 


The  diagonal  (or  " secondary") 
pyramid,  whose  relation  to  the  pri- 
mary pyramid  is  shown  in  Figure  81, 
is  one  whose  parameter  is  2 : 2 :  ix:  2. 


Parameter 

2 : 2 :  ij :  2 


+CC 


-a. 


FIG.  81. — Basal  section  show- 
ing relation  of  primary,  second- 
ary, and  dihexagonal  pyramids 
andprisms.  I=(ioTi),II=(ii2i). 
111=  (2131). 


Ratio 
I    I    I    I 
l'l*2*I 


FIG.  82. — Model  of    a    dihex- 
agonal bipyramid. 

Symbol 
(II2I) 


GUIDE  TO  MINERAL  COLLECTIONS 


The  dihexagonal  pyramid  (Fig.  82)  is  a  form  whose  parameter 


may  be  ^3: 1:3. 


Parameter 

3 


Ratio 

a  b  a*  c 


Symbol 
(2131) 


FIG.  83. — Model  of  a  primary  hexag- 
onal prism. 


FIG.  84. — Secondary  hexagonal  prism 


FIG.  85.— Model  of  a  dihex- 
agonal prism. 


The  relation  of  all  three  of  these 
pyramids  to  each  other  is  shown  by  a 
ground  plan  of  the  lateral  axes  (Fig.  81). 
The  c  axis  is  simply  a  point. 

The  three  prisms  are  similar  and 
their  symbols  are  identical  with  those 
of  the  three  pyramids,  save  that  the 
number  applied  to  the  c  axis  is  always 
zero  (see  Figs.  83,  84,  85). 

Two  hemihedral  forms  are  common; 
first,  that  which  results  when  the  unit 
pyramid  planes  in  alternate  sextants 
only  are  developed.  If  the  start  is  made 


with  the  front  sextant  (noi),  a  positive  rhombohedron  (R)  results 
(Fig.  86).     If  the  start  is  made   with   (oiii),  a  negative  rhombo- 


SULPHANTIMONITES,  SULPHARSENITES  71 

hedron  (—  R)  is  produced.     If  the  two  planes  in  each  alternate  sextant 
of  a  dihexagonal  pyramid  are  developed,  a  scalenohedron  is  formed 


FIG.  86. — Rhombohedron  (R)  resulting 
from  disappearance  of  darkened  planes  of 
the  interior  figure — a  hexagonal  bipyramid. 


FIG.    87. — Model    of    a    positive 
scalenohedron. 


FIG.  88. — Model  of  a  scalenohedron          FIG.  89. — Model  of  a  prism  truncated 
truncated  by  a  rhombohedron  (R).  by  negative  %R. 

(2131)  (Fig.  87).  A  positive  rhombohedron  and  scalenohedron  are 
united  in  Figure  88,  while  in  Figure  89  a  prism  is  truncated  by 
the  negative  \  rhombohedron,  —  \R. 


GUIDE  TO  MINERAL  COLLECTIONS 


FIG.  90. — Pyrargyrite,  crystal 
form. 


Crystals  of  pyrargyrite  and  proustite  occur  in  forms  which  are 
combinations  of  the  secondary  prism  (1120)  terminated  above  with 
the  plus  rhombohedron  (1011),  the  flat  minus  rhombohedron  (0112), 
and  the  flat  scalenohedron  (2134),  while  below  appear  the  scaleno- 
hedrons  (213!)  and  the  rhombohedrons  (011:2)  and  (0114)  (Fig.  90). 

As    usual    with    most    minerals,    well- 
developed  crystals  are  rare.     Ordinarily 
pyrargyrite  and  proustite  occur  in  masses. 
Pyrargyrite  varies  in  color  from  the 
darkest  varieties,  which  are  of  a  deep 
ruby  shade  in  thin  splinters,  to  the  light- 
est varieties,  which  are  clear  wine  color. 
Upon    exposure    to    light,    pyrargyrite 
becomes  dead  black.     It  should  therefore 
be  sheltered  from  light  if   the  reddish 
color  is  to  be  preserved.     The  streak  of 
pyrargyrite  is  purplish  red,  while  that  of 
proustite  is  scarlet. 
Like  minerals  in  all  systems  other  than  the  regular,  these  minerals 
divide  entering  light  into  two  rays  vibrating  at  right  angles  to  each 
other  and  hence  differently  refracted.     One  of  the  rays  is  called  the 
ordinary  (w)  and  the  other  the  extraordinary  (e). 

SUMMARY 

Pyrargyrite. — Ag3SbS3 ;  Ag  =  59 . 8  per  cent,  Sb  =  2  2 .  5  per  cent,  8=17.7 
percent.  Hexagonal;  ditrigonal  polar  (tourmaline  class) ;  0:^=1:0.789; 
(1120),  (1161),  (0112),  (2131),  (2134),  (0114);  massive.  Cleavage  imperfect 
(1161)  and  (1010);  brittle;  fracture  conchoidal. 

Hardness  =2.  5;  gravity  =5. 8.  Black  to  ruby,  streak  purplish  red; 
metallic;  adamantine;  translucent.  Refraction  strong;  mean  refractive 
index  in  sodium  light  is  2 . 98  (stronger  than  that  of  diamond,  and  surpassed 
by  cinnabar  alone,  3.02). 

Easily  fusible;  soluble  in  nitric  acid. 

Guanajuato,  Mexico;  Chili;  Cordilleran  states. 

Proustite. — Ag3AsS3;  Ag  =  69-4  per  cent,  As  =15.  2  per  cent,  8=19.4 
per  cent.  Crystallography  similar  to  pyrargyrite ;  a :  c  =  i :  o .  304. 

Physical  properties  similar  to  pyrargyrite,  but  color  lighter  and  streak 
scarlet.  (0=2.94. 

Localities  similar  to  pyrargyrite. 


SULPHANTIMONITES,  SULPHARSENITES 


73 


TETRAHEDRITE  GROUP 

•In  this  group  are  two  well-crystallized  copper  minerals,  tetra- 
hedrite  (Cu3SbS3)  and  tennantite  (Cu3AsS3),  which  are  related  to 
each  other  as  were  the  two  silver  minerals,  pyrargyrite  and  proustite. 
So  definite  are  they  in  crystal  habit  that  they  have  been  chosen 
to  furnish  the  name  of  a  crystal  class,  the  tetrahedrite  class  (already 
illustrated  by  the  diamond). 

The   tetrahedron   (in)    is  always   developed,  sometimes   alone 
(Fig.  91),  but  usually  combined  with  other  tetrahedrons,  trapezo 
hedrons,  and  dodecahedrons.     A  common  combination  is  a  positive 


111-2 


110 


110 

111 


FIG.  91. — Prevailing  form  of  tetra- 
hedrite. 


FIG.     92. — Characteristic 
tetrahedrite. 


form     of 


tetrahedron  (in)  with  edges  beveled  by  positive  and  negative  three- 
faced  tetrahedrons  (211),  and  with  corners  truncated  by  the  minus 
tetrahedron  (111)  and  beveled  by  the  dodecahedron  (no)  (Fig.  92). 
The  negative  tetrahedron  appears  as  a  small  triangle  on  each  corner 
and  is  usually  dull  or  pitted  with  triangular  markings,  while  the 
positive  faces  are  bright. 

When  complementary  forms  of  a  three-faced  tetrahedron  (211) 
are  present,  the  positive  form  is  often  striated  perpendicularly,  while 
the  negative  is  striated  parallel  to  the  dodecahedron  edge  which  it 
truncates. 

The  edges  and  corners  of  one  tetrahedrite  crystal  often  project 
from  the  faces  of  another — a  kind  of  twinning  derived  by  a  half-turn 
of  the  projecting  crystal  about  a  line  normal  to  (in). 

In  tennantite,  dodecahedral  or  cubic  faces  usually  predominate 
(Fig.  93). 


74 


GUIDE  TO  MINERAL  COLLECTIONS 


The  old  German  miners  called  both  of  these  minerals  (tetrahedrite 
and  tennantite)  Fahlerz  ("pale  ore"),  and  that  term  included  several 
varieties  which  were  later  divided  and  named  according  to  the  locality 
in  which  they  are  found  or  according  to  some  peculiarity  due  to 
varying  composition.  They  contain  not  only  copper,  antimony, 
arsenic,  and  sulphur,  but  of  ten.  bismuth,  lead,  silver,  mercury,  zinc, 
and  iron  in  varying  amounts,  vicariously  replacing  each  other. 

Some  of  the  varieties  are  the  following:  (i)  freibergite  (Freiberg, 
Saxony)  often  contains  as  much  as  30  per  cent  of  silver  and  is 
lighter  than  ordinary  tetrahedrite  in  color;  (2)  schwatzite  (Schwatz, 


FIG.  93. — Tennantite  (schwatzite) 


FIG.  94. — Model  of  sandbergerite 


Tyrol)  contains  16  per  cent  mercury  and  occurs  in  black,  drusy, 
dodecahedrons;  (3)  binnite  (Binnenthal,  Switzerland)  appears  in 
brilliant  cubic  crystals;  (4)  sandbergerite  contains  zinc  and  shows  a 
tendency  to  develop  large  faces  of  the  three-faced  tetrahedron 
(211)  (Fig.  94). 

Tetrahedrite  crystals  are  often  coated  with  brassy,  drusy  chal- 
copyrite  (Cornwall).  They  can  all  be  recognized  by  polar  symmetry, 
metallic  luster,  absence  of  cleavage,  and  reactions  for  copper,  together 
with  either  arsenic  or  antimony. 

Massive  tetrahedrite  is  worked  in  Germany,  Cornwall,  and  in 
many  places  in  the  Cordilleran  states  as  a  source  of  copper  and 
silver. 


SULPHANTIMONITES,  SULPHARSENITES 


SUMMARY 


75 


Tetrakcdrite.—Cu3SbS3;  Cu  =  46.8  per  cent,  Sb=2g.6  per  cent, 
8  =  23.6  per  cent.  Regular;  symmetry  ditrigonal  polar;  (in),  (ni), 
(no),  (211);  twinning  axis  the  normal  to  (in);  brittle;  fracture  sub- 
conchoidal. 

Hardness  =  3. 5;  gravity  =  4. 7.  Lead  gray;  streak  dark  brown; 
metallic;  opaque. 

Fusible;  soluble  in  nitric  acid. 

Germany,  Bohemia,  Cornwall,  western  United  States. 


CLASS  IV.    HALOIDS 
THE  SALT  GROUP 

The  two  most  important  minerals  of  this  group  are  halite,  sodium 
chloride  (common  salt),  and  sylvite,  potassium  chloride.  Being  sol- 
uble in  water,  they  may  be  distinguished  by  their  taste.  While  both 
are  saline,  sylvite  is  bitter. 

Sylvite — the  sal  digestivus  syfoii  of  the  old  pharmacists — has  long 
been  used  for  medicinal  and  chemical  purposes.  It  was  first  dis- 
covered in  the  volcanic  sublimations  of  Vesuvius,  but  larger  quan- 
tities and  finer  specimens  are  now  obtained  at  Stassfurt,  Germany. 

Halite  has  the  distinction  of  being  the  mineral  most  largely  used 
as  a  food.  Other  minerals  furnish  food  for  plants  and  thus  indirectly 
sustain  the  life  of  man,  but  halite  is  the  only  mineral  which  is  eaten 
in  its  natural  state.  It  is  also  one  of  the  most  useful  of  minerals  in 
chemical  and  manufacturing  industries — glass  manufacture,  chlorine 
and  soda  works,  etc. 

Halite  is  the  most  abundant  salt  in  ocean  water,  and  in  many 
seas  in  arid  regions  in  various  parts  of  the  world.  Salt  Lake,  Utah, 
contains  20.19  Per  cent  sodium  chloride;  the  Dead  Sea,  Palestine, 
only  7  .8  per  cent.  The  Dead  Sea  contains  more  magnesium  chloride, 
about  1 1  per  cent,  and  about  2  per  cent  of  potassium  chloride.  Its 
total  content  of  salts  exceeds  that  of  Salt  Lake,  being  about  25  per 
cent. 

By  the  evaporation  of  such  seas  in  preceding  geological  periods, 
great  beds  of  salt  have  been  laid  down.  Such  are  those  of  New  York, 
Michigan,  Louisiana,  Kansas,  Nevada,  and  other  states.  The  New 
York  bed  most  utilized  is  seventy-five  feet  thick  and  lies  at  a  depth 
of  from  one  thousand  to  two  thousand  feet  below  the  surface.  The 
salt  is  obtained  there,  as  it  is  in  Michigan,  Louisiana,  Kansas,  and 
other  places,  by  driving  pipes  down  to  the  bed,  forcing  hot  water 
down  to  dissolve  the  salt,  and  carrying  the  brine  thus  produced  up  to 
evaporating  basins,  where  it  is  collected,  purified,  and  made  ready  for 
market.  In  some  places  salt  is  mined  just  as  is  coal.  The  great 
chambers  remaining  after  the  removal  of  mountainous  masses  of  salt 

76 


HALOIDS 


77 


in  some  of  the  mines  of  Germany,  Austria,  and  Russia  are  among  the 
most  interesting  and  beautiful  underground  caverns  that  are  to  be 
found. 

Salt  obtained  by  evaporation  of  brines  often  exhibits  skeletal 
cubes  with  cavernous  faces  (Fig.  95).     Natural  crystals  show  quite 
perfect  cubes.     Ordinarily  both  halite  and  sylvite  occur  in  granular 
and   massive   condition    and   contain   mag- 
nesium chloride,  magnesium   sulphate,  and 
calcium  sulphate  as  impurities. 

When  pure,  salt  is  transparent  and  color- 
less. But  varying  tints  of  yellow,  red,  and 
blue  are  common.  The  coloring  material  is 
usually  some  iron  oxide.  It  has  been  sug- 
gested that  the  deep  blue  color  in  salt  (see 
No.  3288  from  Stassfurt)  may  be  due  to 
metallic  potassium. 

Both  halite  and  sylvite  are  highly  dia- 
thermanous,  allowing  free  passage  of  heat 

as  other  transparent  bodies  allow  passage  of  light,  and  cleavage 
blocks  are  used  to  inclose  gases  in  a  tube  with  transparent  ends 
which  will  readily  transmit  heat  rays. 

SUMMARY 

Halite. — NaCl;  Na  =  3Q.4  per  cent,  Cl  =  6o.6  per  cent.  Regular; 
(100);  massive.  Cleavage  perfect  (100) ;  brittle;  conchoidal. 

Hardness  =  2 .  5 ;  gravity  =2.  2.  Colorless;  streak  white;  vitreous; 
transparent;  refraction  weak,  n=  i .  54. 

Soluble  in  three  volumes  of  water;  taste  saline;  fusible. 

Lakes  in  arid  regions,  New  York,  Michigan,  Louisiana,  Kansas,  Ger- 
many, Poland,  Russia. 


FIG.   95. — Halite  cube 
from  salt  brine. 


Sylvite. — KC1;  K  =  52.4  per  cent,  0  =  47.6  per  cent.  Regular;  sym- 
metry holoaxial;  (100);  massive.  Cleavage  perfect  (100);  brittle;  frac- 
ture uneven. 

Hardness=2;  gravity  =1.9.  Colorless;  streak  white;  vitreous; 
transparent;  refraction,  11=1.49. 

Soluble  in  three  volumes  of  water;  taste  saline,  bitter;  fusible. 

Volcanic  regions;  Stassfurt. 


78  GUIDE  TO  MINERAL  COLLECTIONS 

Fluorite 

Fluorite  (CaF2)  occurs  commonly  in  beautiful,  clear-cut  cubic 
crystals.  Few  minerals  show  their  crystal  form  so  plainly.  The 
edges  of  the  cubes  are  often  beveled  by  the  four-sided  cube  (310) 
(Fig.  96)  or  by  a  hexoctahedron  (421)  (Fig.  97).  The  flat  four-faced 
cube  is  so  characteristic  that  it  has  been  called  the  "fluoroid." 

The  most  typical  twinning  of  fluorite  is  that  where  two  cubes 
interpenetrate  about  a  line  normal  to  (in)  with  the  result  that  the 
corners  of  one  cube  project  from  the  faces  of  the  other  (Fig.  98). 
At  a  point  where  these  corners  emerge,  the  cube  face  is  raised  into 
low  "  vicinal"  faces  which  form  a  flat  four-faced  cube  with  very  high 
parameters,  for  example,  32:1:0.  " Vicinal"  faces  often  replace 


FIG.  96.— Fluorite 


FIG.  97. — Fluorite 


simple  faces  with  low  parameters.  Multitudes  of  minute  cubic 
crystals  often  cover  the  faces  of  the  large  cubes  without  detracting 
from  their  luster,  since  the  minute  faces  are  parallel  to  the  large  ones. 
Fluorite  also  occurs  in  granular  and  compact  masses. 

Its  cleavage  is  remarkably  perfect,  yielding  octahedrons  (Plate 
XIII).  This  trait,  together  with  its  vitreous  luster,  aids  in  the  ready 
identification  of  the  mineral.  The  cubic  faces  have  a  higher  luster 
than  have  the  cleavage  faces.  Natural  octahedrons  are  usually  dull. 
Fluorite  displays  many  beautiful  colors.  Large  yellow  cubes  with 
corners  beveled  by  (421)  are  found  at  Mehenoit,  Cornwall;  and 
transparent  yellow  cubes  (see  No.  503),  at  Durham.  Beautiful 
purple  crystals,  No.  502  from  Alston  and  No.  3852  from  Cumberland, 
are  shown.  Pink  and  rose-red  octahedrons  are  found  near  Chamonix, 
and  at  the  island  of  Siglio  (near  Elba).  Beautiful  green,  plum- 


PLATE    XII 


Fluorite  group  from  Rosiclare,  Hardin  County,  Illinois 


PLATE  XIII 


a,  Fluorite  cubes,  Rosiclare,  Illinois 


b,  Octahedrons  cleaved  out  by  ten-year-old  boy,  showing 
ease  and  regularity  of  cleavage. 


HALOIDS 


79 


colored,  and  amethystine  crystals  from  the  north  of  England  adorn 
many  museums.  Since  the  colors  are  in  layers  parallel  to  cubic 
faces,  some  lilac  cubes  have  a  yellow  center  (Derbyshire)  and  some  a 
deep  green  center.  Amethystine  (Nos.  3296  and  3297),  green 
(Nos.  2278  and  2567),  and  colorless  (No.  1788)  specimens,  all  from 
Rosiclare,  Hardin  County,  give  an  idea  of  the  color  of  Illinois  occur- 
rences. Large  crystal  groups  are  shown  in  Nos.  708  and  958. 
No.  908  is  a  typical  massive  specimen.  The  most  complete  exhibit 
of  Illinois  fluorite  is  shown  in 
the  cases  devoted  to  the  eco- 
nomic exhibits. 

When  specimens  of  fluorite 
are  heated,  they  lose  in  weight 
and  color,  and  hence  are  thought 
to  owe  their  color  to  hydro- 
carbon compounds.  No  rela- 
tion has  been  traced  between 
composition  and  color.  Green 
and  red  crystals  are  strongly 
phosphorescent,  that  is,  if  heated 
above  212°  F.  or  held  in  sun- 
light, when  taken  into  a  dark 
room  they  are  luminous.  The 

phenomenon  called   "fluores-  FIG.  98.-Modd  of  fluorite  twin 

cence"     is    named    from    this 

mineral,  since  it  is  best  illustrated  when  some  richly  colored  speci- 
mens are  held  in  the  sunlight.  They  become  hazy  at  a  slight 
depth  below  the  surface  and  diffuse  from  this  superficial  layer  a 
plum-blue  color.  When  viewed  by  transmitted  light,  they  are  light 
green.  This  fluorescence  is  due  to  transformation  of  light  rays  within 
the  mineral,  so  that  those  emitted  are  of  greater  wave-length  than 
those  which  entered. 

Fluorite  is  low  in  refraction  («  =  i  .43).  Were  colorless  iso tropic 
crystals  more  abundant,  the  mineral  would  find  extensive  use  in  the 
manufacture  of  lenses  and  microscopic  objectives  where  achromatic 
light  is  desired.  It  is  used  in  the  production  of  ultra-violet  rays,  for 
making  vases  and  ornaments  (Derbyshire,  England),  and  for  enamel 
and  glass  manufacture;  but  the  largest  quantities  are  employed  as  a 


8o  GUIDE  TO  MINERAL  COLLECTIONS 

flux  in  iron  smelting  and  in  similar  operations  where  a  fluid  slag  is 
sought. 

Being  the  only  common  mineral  which  contains  fluorine  in  any 
large  proportion,  fluorite  is  the  chief  source  of  hydrofluoric  acid. 
Moissan  used  it  for  vessels  and  stoppers  in  experiments  on  the  isola- 
tion of  fluorine,  since  it  is  one  of  the  few  substances  which  is  not 
attacked  by  the  gas. 

Fluorite  occurs  chiefly  associated  with  metallic  ores,  calcite, 
barite,  and  in  tin-bearing  veins  which  are  marked  by  the  presence  of 
other  minerals  containing  fluorine,  such  as  topaz,  lepidolite,  tourma- 
line, and  apatite.  Illinois  leads  all  other  states  in  the  production  of 
fluorite,  some  years  more  than  a  million  dollars'  worth  having  been 
sold,  greatly  to  the  advantage  of  the  steel  industry,  the  manufacture 
of  enameled  bath  tubs,  the  production  of  hydrofluoric  acid,  etc. 

SUMMARY 

Fluorite. — CaF2;  Ca=5i.i  per  cent,  F  =  48.g  per  cent.  Regular; 
holosymmetric;  (100),  (310),  (421).  Massive;  interpenetrant  twins  on 
axis  normal  to  (in).  Cleavage,  perfect  (in);  brittle;  fracture  sub- 
conchoidal. 

Hardness  =  4;  gravity  =  3. 2.  Purple,  blue,  green,  yellow,  brown; 
streak  white;  vitreous;  transparent.  Refraction  weak  (to  =1.44);  dis- 
persion weak. 

Fusible;  soluble  in  nitric  acid. 

England,  Germany,  France,  Illinois,  Kentucky,  Colorado. 

Cryolite 

Cryolite  is  a  colorless  or  pure  white  translucent  mineral  composed 
of  sodium  and  aluminium  fluoride  (Na3AlF6).  It  is  well  named  "  ice- 
stone"  (xpvos,  " frost"  and  \ldos,  " stone")  because  of  the  trans- 
lucence  of  its  white  masses,  because  of  its  low  melting-point  (a 
splinter  fuses  in  a  candle  flame),  and  because  it  has  been  obtained  in 
the  greatest  amounts  in  the  land  of  ice,  West  Greenland,  where  it  was 
discovered  near  the  town  of  Ivigtut  in  1795.  It  was  long  the  only 
source  of  aluminium  and  is  still  an  important  ore,  though  today 
bauxite,  a  brownish,  earthy,  hydrated  aluminium  oxide  (A12O3+2H2O) 
found  in  quantities  in  the  southern  states,  furnishes  most  of  the  alu- 
minium of  commerce.  Free  crystals  of  cryolite  are  so  rare  that 
the  author  has  never  noticed  one.  Optical  examination  of  crystalline 


HALOIDS  81 

masses  and  etching  with  sulphuric  acid,  however,  show  the  crystals  to 
be  repeatedly  twinned  and  to  belong  to  the  "triclinic  system."  In 
masses  they  resemble  cubes  placed  in  parallel  position.  Their  cleav- 
age also  appears  to  be  parallel  to  cubic  planes,  hence  it  is  easy  to 
mistake  their  crystallography. 

The  cleavage,  oblique  stria tions,  and  hardness  (2.5)  distinguish 
cryolite  from  colorless  fluorite  and  similar  minerals.  Heated  with 
sulphuric  acid,  cryolite  gives  off  hydrofluoric  acid  (HF). 

SUMMARY 

Cryolite. — Na3AlF6j  Na=32.8  per  cent,  Al=i2.8  per  cent,  F~ 54.4 
per  cent.  Triclinic;  (no),  (ooi),  (101);  massive;  cleavage,  perfect, 
parallel  (ooi),  nearly  perfect  parallel  (no),  (101) ;  brittle;  fracture 
uneven. 

Hardness  =  2 .  5 ;  gravity  =  3.  Colorless;  vitreous;  transparent;  refrac- 
tion weak,  /3=i.36;  birefringence  weak,  positive. 

Easily  fusible;  soluble  in  sulphuric  acid. 

Greenland. 


CLASS  V.    OXIDES 

Of  the  minerals  which  consist  of  one  or  more  basic  elements 
united  with  oxygen,  about  seventeen  are  abundant  and  important. 
The  oxides  of  silicon,  that  is,  quartz,  chalcedony,  and  opal,  will  be 
considered  first;  and  second,  the  oxides  of  the  metals,  such  as  cu- 
prite, zincite,  corundum,  hematite,  spinel,  magnetite,  franklinite, 
chromite,  cassiterite,  rutile,  pyrolusite,  manganite,  goethite,  and 
limonite,  will  be  taken  up  next. 

Quartz 

Quartz  (SiO2)  is  the  most  abundant  mineral  in  the  world.  It  is 
the  chief  constituent  in  the  sands  of  the  deserts  and  of  the  ocean 
shores,  in  the  great  layers  of  sandstone  and  quartzite  which  underlie  the 
plains  and  outcrop  in  the  mountains,  and  in  most  of  the  rocks  that 
form  the  cores  of  mountain  ranges. 

No  mineral  has  received  more  study  than  quartz.  It  furnished 
that  thoughtful  Danish  physician,  theologian,  and  geologist,  Steno 
(1669),  material  with  which  to  establish  the  "law  of  the  constancy  of 
a  crystal  angle,"  and  it  has  been  the  subject  of  study  for  mineralogists 
ever  since,  seeming  still  to  be  able  to  reward  the  investigator  with 
new  facts. 

The  Greeks  thought  quartz  to  be  ice  so  thoroughly  frozen  as  to 
have  lost  the  power  of  melting,  and  hence  named  it  Kpuo-raXXos,  that 
is,  "ice,"  and  today  many  persons  say  crystal  when  they  mean 
quartz.  The  name  "quartz"  is  an  old  German  mining  term  used 
since  the  sixteenth  century  and  now  common  to  many  languages. 

Crystals  of  quartz  are  more  abundant  than  those  of  any  other 
mineral.  They  occur  in  the  hexagonal  system,  and  their  symmetry 
is  trigonal  holoaxial,  i.e.,  they  have  no  plane  nor  center  of  symmetry 
but  if  revolved  around  the  c  axis  their  planes  occupy  similar  positions 
three  times  during  a  complete  revolution. 

Prism  (loio)  and  rhombohedron  (1011)  planes  are  nearly  always 
present  and  combined,  as  shown  in  Figure  99.  In  Hungary  and 
Brazil  are  found  crystals  which  contain  these  planes  only.  It  will  be 
seen  that  when  revolved  around  the  c  axis  an  upper  rhombohedron 

82 


PLATE  XIV 


a,  Smoky  quartz,  "cairn- 
gorm," from  Montana. 


b,  Quartz,  Montgomery  County,  Arkansas 


PLATE  XV 


Quartz  group,  Montgomery  County,  Arkansas 


OXIDES  83 

would  be  in  the  front  three  times  during  a  complete    revolution; 
hence  the  crystals  are  "trigonal." 

Several  planes  occur  with  such  regularity  that,  for  sake  of  abbre- 
viation, to  represent  them  a  letter  is  used  instead  of  the  symbol,  for 


FIG.  ioo. — Quartz 


FIG.  99. — Quartz;  prism  and  rhombo- 
hedron. 


FIG.  101. — A  form  of  quartz  common 
at  Alston  Moor,  England. 


FIG.  102. — Quartz 


example,  R  stands  for  the  plus  rhombohedron  (ion),  z  for  the  minus 
rhombohedron  (oin),  m  for  the  prism  (1010),  5  for  the  right  trigonal 
pyramid  (1121),  and  x  for  the  right  plus  trapezohedron  (5161)  (Figs. 
100-102).  The  construction  of  the  right  and  left  plus  trapezohedrons 


84  GUIDE  TO  MINERAL  COLLECTIONS 

is  explained  below  (see  Figs.  103  and  104).  Rarely  is  a  crystal  termi- 
nated by  a  single  rhombohedron,  as  in  Figure  102.  The  usual 
termination  is  a  combination  of  plus  and  minus  rhombohedrons, 
R  (ion)  and  z  (om),  of  different  sizes.  Sometimes  R  and  z  are 
so  nearly  of  the  same  size  as  to  resemble  a  unit  pyramid  (Fig.  101). ' 

In  some  crystals,  like  those  from  Alston  Moor,  England,  the 
prism  planes  are  very  small  or  disappear,  and  the  result  resembles  a 
bipyramid  (Fig.  101).  But  their  trigonal  character  can  be  discovered 
by  heating  them  and  plunging  them  into  water,  when  they  cleave 


FIG.  103. — Quartz;  positive  left  trig-          FIG.    104. — Quartz;     positive    right 
onal  trapezohedron.  trigonal  trapezohedron 

into  imperfect  rhombohedra.  In  some  crystals  the  right  edge  between 
R  and  m  is  truncated  by  the  plane  5  whose  symbol  is  (1121)  (Fig.  102). 
It  has  the  direction  of  the  diagonal  pyramid,  yet  occurs  but  three  times 
instead  of  six,  so  is  recognized  as  a  hemihedral  form  of  the  diagonal 
pyramid  called  the  "right  trigonal  pyramid."  The  left  trigonal 
pyramid  appears  on  the  left-hand  side.  The  trigonal  pyramid  is 
often  accompanied  by  a  trapezohedral  face  x  (5161).  Figures 
103  and  104  show  right-handed  and  left-handed  trapezohedrons. 
They  result  when  the  alternate  upper  sextants  of  a  scalenohedron 
and  the  corresponding  sextant  below  are  developed.  The  trapezo- 
hedral planes  are  marked  by  the  letter  x.  The  right-  and  left- 
handed  crystals  may  be  distinguished  in  three  ways:  first,  in  a 


PLATE  XVI 


Quartz,  Bourg  de  Oisans  twin,  Hot  Springs,  Arkansas 


OXIDES 


right-handed  crystal  the  x  plane  is  below  the  right-hand  corner  of  the 
rhombohedron;  second,  the  direction  of  the  zone  z  s  x  m  is  that  of 
the  thread  of  a  right-handed  screw;  and  third,  the  striae  on  s  are 
parallel  to  the  edge  sR. 

Twinning  in  quartz  crystals  is  common  according  to  three  laws: 
first,  two  crystals  of  the  same  sort,  both  right-handed  or  left-handed, 
may  be  united  parallel  to  the  c  axis  in  interpenetrant  twins  (Fig.  105). 
Thus  x  may  appear  at  each  corner  and  R  and  z  in  the  same  plane. 
However,  since  R  is  usually  smooth  and  bright,  while  z  is  pitted  or 


X- 


K 


FIG.  1 05 .— T wo  right-handed  quartz 
crystals  twinned  parallel  to  c  axis. 


X  - 


FIG.  106. — Brazil  twin.  Right-  and 
left-handed  quartz  crystals  interpene- 
trating. 


coated,  they  may  be  distinguished  from  each  other.  The  boundaries 
of  the  two  interlacing  crystals  show  a  zigzag  pattern.  Second,  right- 
handed  and  left-handed  crystals  interpenetrate  parallel  to  the  c  axis 
and  at  the  same  time  parallel  to  the  diagonal  prism  (1120).  In  this 
case  twinning  is  betrayed  by  the  x  and  z  faces  (Fig.  106).  This  is 
called  the  Brazil  twin.  Figure  107  shows  two  right  juxtaposed  Brazil 
twins.  Third,  Bourg  de  Oisans  in  Dauphiny  (France)  has  long  been 
noted  for  fine  quartz  crystals  twinned  in  the  manner  shown  in  Figure 
108  (Nos.  3307,  3308,  and  3315).  Recently  Japan  has  furnished  the 
museums  of  the  world  with  a  large  number  of  these  twins.  They 
are  united  parallel  to  the  diagonal  pyramid  (1122)  so  that  the  c  axis 
and  the  line  of  union  form  a  zigzag. 


86 


GUIDE  TO  MINERAL  COLLECTIONS 


Quartz  illustrates  not  only  the  geometrical  but  the  optical,  elec- 
trical, thermal,  and  chemical  features  of  crystals  as  well.  Optical 
properties  throw  much  light  upon  its  internal  structure.  The  con- 
nection between  geometrical  and  electrical  properties  may  be  illus- 
trated as  follows:  The  three  horizontal 
axes  are  polar  (i.e.,  not  symmetrical 
around  the  center),  for  one  end  of  each 
axis  emerges  through  a  prism  edge  that 
is  truncated  by  the  planes  5  and  x,  and 
the  other  through  a  prism  lacking  these 
planes.  Since  the  horizontal  axes  are 
polar,  they  exhibit  pyro-electric  polarity. 
Finely  powdered  red  lead  and  sulphur 
are  sifted  through  a  piece  of  cloth,  thus 
becoming  electrified  by  friction.  The 
red  lead  is  positive,  the  sulphur  negative. 
When  they  touch  the  heated  quartz  crys- 
tal, the  s  and  x  faces  become  negatively 
electrified  on  cooling,  i.e.,  attract  the 
red  lead. 


FIG.  107. — Brazil  twin.  Two 
right-handed  crystals  juxta- 
posed. 


A 


B 


FIG.  108.  —  Quartz  twinned  on 
(1122).     Bourg  de  Oisans  twin. 


FIG.  109.  —  Quartz  etched  with  hydrofluoric 
acid;   A,  left-handed;    B,  right-handed. 


The  action  of  caustic  alkalies  or  hydrofluoric  acid  in  nature  or  in 
the  laboratory  produces  different  effects  on  different  planes,  and  thus 
the  right-handed  and  left-handed  nature  of  the  crystals  can  be  made 
evident  (Fig.  109).  The  etching  shows  that  the  forms  are  related  to 
each  other  as  are  a  right  and  left  glove,  and  hence  they  are  said  to 
be  entantiomorphous. 


OXIDES  87 

The  manner  of  crystal  growth  is  shown  by  some  specimens  of 
quartz  which  within  the  transparent  outer  crystal  have  different  layers 
of  cloudy  material  forming  outlines  of  the  planes  at  different  stages  of 
the  crystal's  development.  This  is  called  "ghost  quartz."  "Capped 
quartz"  has  an  inner  kernel  separated  from  the  outer  by  a  layer  of 
clay  or  other  substance  which  permits  them  to  be  taken  apart. 
"Twisted  quartz,"  while  seeming  to  consist  of  a  single  warped  crystal, 
in  reality  is  composed  of  many  individuals,  each  turned  through  a 
small  angle  so  as  to  produce  a  spiral  effect.  Quartz  is  practically 
lacking  in  cleavage.  Only  by  heating  and  plunging  in  cold  water  can 
rough  rhombohedrons  be  obtained. 

Intergrowths  of  right-  and  left-handed  quartz  break  with  a  wavy 
surface,  producing  "ripple  fracture,"  while  the  ordinary  fracture  is 
conchoidal. 

As  might  be  expected  in  a  mineral  so  abundant  and  so  varied  in 
its  surroundings  and  mode  of  formation,  quartz  exhibits  great  variety 
in  form  and  appearance. 

Rock  crystal,  or  mountain  crystal,  as  it  was  called  by  indefatigable 
collectors  who  sought  fine  specimens  in  the  mountain  fastnesses  of 
Switzerland  and  the  Tyrol,  is  a  clear,  transparent  variety  well  marked 
in  crystallization.  It  was  formed  in  non-resistant  rocks  like  clay 
and  sandstone,  or  in  cavities  in  igneous  or  metamorphic  rocks,  which 
afforded  it  opportunity  to  develop  its  own  planes  (see  Nos.  1772  to 
1779,  3896,  etc.).  Crystals  of  remarkable  size  have  been  found  in  the 
Alps,  Brazil,  Japan,  and  Madagascar.  'A  crystal  twenty-five  feet  in 
circumference  was  found  in  Madagascar.  A  famous  cave  in  the 
Berner  Oberland  in  Switzerland  yielded  five  hundred  tons  of  quartz 
crystals.  Herkimer  County,  New  York,  is  noted  for  its  beautiful, 
transparent  crystals.  Little  Rock,  Arkansas,  has  annually  furnished 
countless  souvenirs  of  this  kind  to  the  tourists  in  that  region  (Nos.  473, 
1775,  etc.).  Multitudes  of  geodes  found  at  Warsaw  in  Hancock 
County,  Illinois,  varying  in  size  from  a  hazelnut  to  nodules  a  foot  or 
more  in  diameter  are  lined  with  clear  quartz  crystals.  There  is 
hardly  a  state  in  the  United  States  in  which  fine  quartz  crystals 
have  not  been  found. 

Clear  crystals  have  long  been  used  for  ornaments.  Beautiful 
transparent  globes  as  much  as  six  inches  in  diameter  have  been  cut 
from  quartz  found  in  Japan. 


88 


GUIDE  TO  MINERAL  COLLECTIONS 


Inclosures  of  foreign  substances  may  add  to  the  beauty  of  the 
mineral.  Crystals  from  Herkimer  County,  New  York,  often  inclose 
anthracite  flakes.  Spangles  of  mica  and  of  hematite  produce  the 
shimmer  seen  in  aventurine  quartz.  Fibrous  actinolite,  asbestos,  or 
rutile  needles  produce  beautiful  effects.  Silky  fibers  of  asbestos  or  of 
quartz  replacing  them  give  a  peculiar  band  of  color  to  the  opalescent 
quartz  called  "cat's  eye"  (a  name  more  properly  applied  to  a  variety 
of  chrysoberyl) .  The  golden  yellow  crocidolite  from  South  Africa 
owes  its  beauty  to  this  cause.  Cavities  shaped  like  a  quartz  crystal 

and    containing   water   or   liquid 
carbon  dioxide  are  often  seen. 

There  are  several  varieties 
based  on  color:  milk  quartz  (No. 
1773)  is  white  and  opaque,  morion 
(No.  4645)  is  black,  smoky  quartz 
(No.  3312)  brown.  Morion  and 
smoky  quartz,  abundant  in  the 
Alps,  are  colored  by  a  hydro- 
carbon which  disappears  upon 
heating.  When  cut  into  gems 
smoky  quartz  is  called  "cairn- 
gorm." A  clear  yellow  quartz 
also  colored  by  hydrocarbon  is 
named  citrine.  Prase  (No.  3225) 

is  green  from  needles  of  actinolite.  Rose  quartz  abundant  in  the 
Black  Hills  is  pale  red  from  solution  of  salts  of  titanium  or  man- 
ganese (Nos.  1681,  3323,  4513).  Amethyst,  a  violet  quartz,  has 
long  been  one  of  the  most  popular  of  semiprecious  stones  (Nos.  4458, 
588,  589,  3319,  etc.).  Its  color  is  thought  to  be  due  to  manganese, 
though  upon  heating  to  a  temperature  of  250°  it  changes  to  yellow. 
The  color  is  often  irregularly  distributed,  white,  opaque  layers  alternat- 
ing with  transparent  violet  and  brown  layers  (Plate  XVII).  Micro- 
scopic examination  shows  alternating  layers  of  right-  and  left-handed 
lamellae.  Where  the  right  and  left  layers  are  mingled,  converging 
light  produces  lines  known  as  "Airy's  spirals"  (Fig.  no).  The 
interpenetration  of  right-  and  left-handed  layers  produces  roughly 
striated  surfaces.  The  more  strongly  colored  parts  are  "biaxial," 
that  is,  they  have  two  directions  in  which  light  is  not  doubly  refracted. 


FIG.    no. — Airy's   spiral   in   right- 
handed  crystal. 


PLATE  XVII 


Amethyst,  Thunder  Bay,  Lake  Superior 


OXIDES  89 

Upon  heating,  the  biaxial  character  disappears,  showing  that  it,  as 
well  as  the  color,  is  due  to  easily  destructible  material.  Beautiful 
violet  specimens  are  found  in  Brazil,  Ceylon,  the  Urals,  Colorado, 
and  north  of  Lake  Superior.  By  some  authors  all  quartz  showing 
Airy's  spirals  is  called  amethyst,  whatever  the  color. 

Quartz  quite  commonly  replaces  organic  substances,  producing 
such  objects  of  permanent  beauty  as  silicified  wood;  or  fills  cavities 
formerly  occupied  by  fluorite,  calcite,  barite,  etc.,  assuming  the  shape 
of  these  minerals,  thus  producing  pseudomorphs.  A  cube  of  quartz 
may  be  a  pseudomorph  after  fluorite;  fibrous  quartz,  a  pseudomorph 
of  fibrous  gypsum;  cellular  quartz,  the  capping  of  calcite  crystals 
later  dissolved  by  water.  Quartz  is  the  great  repairing  agent  of 
nature,  since  it  so  commonly  cements  crevices  in  rock  layers  and 
microscopic  fissures  in  minerals. 

SUMMARY 

Quartz. — SiO2;  Si=46.y  per  cent,  0  =  52.3  per  cent.  Hexagonal; 
symmetry,  trigonal  holoaxial  (quartz  class).  a:c=i:i.i.  w=(ioio), 
R=(ioii),  2=(oiii),  s=(ii2i),  #=(5161).  Twinned  on  m  (1010)  or 
(1122).  Massive,  cleavage  parallel  R  very  imperfect;  brittle;  fracture 
conchoidal. 

Hardness=y;  gravity  =2. 65.  Colorless;  vitreous;  transparent, 
0^=1.544.  Uniaxial;  double  refraction,  positive  weak;  rotary  polariza- 
tion, strong. 

Infusible  before  blowpipe;  insoluble  in  acid. 

Ubiquitous. 

Chalcedony 

Chalcedony  is  identical  with  quartz  in  chemical  composition  and 
in  many  physical  properties,  but  differs  in  several  respects.  First,  it 
never  shows  crystal  planes  but  occurs  in  translucent  or  opaque 
botryoidal,  reniform,  or  stalactitic  masses  composed  of  microscopic 
fibers.  Second,  the  fibers  composing  it  are  optically  biaxial.  Quartz 
is  uniaxial.  The  refractive  index  and  fusing-point  of  chalcedony 
differ  from  those  of  quartz. 

Chalcedony  is  waxy  or  greasy  in  luster,  and  somewhat  splintery  in 
fracture.  It  is  much  more  soluble  in  potassium  hydrate  than  is  quartz. 
It  is  deposited  from  aqueous  solution,  and  is  found  in  veins  or  other 
cavities  in  various  kinds  of  rocks.  Usually  it  has  banded  structure 


90  GUIDE  TO  MINERAL  COLLECTIONS 

and  shows  a  great  variety  of  colors.  The  banding  is  due  to 
alternation  of  different-colored  layers  of  chalcedony,  quartz,  and 
opal. 

There  are  many  varieties.  The  translucent,  waxy,  cream- 
colored,  slightly  banded  variety  is  chalcedony  proper.  The  red 
variety  is  called  carnelian;  the  brownish-red,  sard;  the  leek-green, 
plasma;  the  apple-green,  chrysoprase  (No.  3324);  chalcedony  with 
blood-red  spots  of  jasper,  heliotrope  (No.  3329).  Agate  (Nos.  496- 
99,  etc.)  is  composed  of  successive  bands  of  chalcedony,  carnelian, 
jasper  (No.  568),  smoky  quartz,  amethyst,  etc.,  that  have  been  laid 
down  in  the  lining  of  a  cavity,  the  outer  band  being  formed  first  and 
the  others  successively  until  the  cavity  has  been  more  or  less  filled. 
Usually  the  last  stages  permit  of  the  formation  of  good  quartz  crystals. 
The  fineness  of  some  of  the  layers  is  a  cause  of  wonder,  and  as  the 
cavities  often  have  no  visible  outlet,  the  manner  in  which  the  silicon 
reached  its  resting-place  is  enigmatical  unless  it  be  explained  as  being 
due  to  the  solidification  of  colloidal  silica.  Sometimes  the  solution 
has  deposited  curvilinear  layers  first,  and  later  parallel  bands  per- 
fectly horizontal  (No.  496).  Such  deposits  are  prized  for  cameo 
cutting.  The  figure  is  cut  in  one  layer  and  the  background  in  a  layer 
of  different  color.  When  the  layers  are  black  and  white,  the  material 
is  called  onyx.  When  red  or  brown,  sardonyx.  In  moss  agate 
(Nos.  4398  and  1851),  banding  is  inconspicuous,  but  dendritic  inclu- 
sions of  chlorite,  manganese  oxide,  and  other  substances  occur. 
Flint  (No.  3330)  is  a  translucent  to  gray,  brown,  or  nearly  black  chal- 
cedony consisting  largely  of  the  remains  of  diatoms,  sponges,  and 
other  marine  organisms.  The  best  variety  is  found  in  the  chalk 
cliffs  of  England.  Hornstone,  as  its  name  implies,  resembles  horn  in 
color  and  in  streaked  appearance.  It  is  more  brittle,  splintery,  and 
soluble  than  flint,  and  less  pure.  Chert  is  still  farther  removed  from 
flint  in  these  respects.  Its  color  is  white  or  gray,  and  the  impurities 
are  calcareous  and  arenaceous  substances.  Jasper  is  a  creamy, 
brown,  or  red  chalcedony  containing  ferruginous,  calcareous,  or 
arenaceous  substances  as  impurities. 

These  last  four-named  varieties  border  very  closely  upon  rock 
species  because  of  their  impurities.  A  final  step  is  represented  by 
granular  to  massive  silica,  which  occurs  in  large  bodies  and  forms  the 
rock  called  quartzite. 


PLATE  XVIII 


Moss  agate,  India 


OXIDES  91 

SUMMARY 

Chalcedony. — SiO2;  81=46.7  per  cent,  0  =  53.3  per  cent.  Crypto- 
crystalline,  apparently  amorphous,  concretionary,  botryoidal,  stalactitic, 
arborescent.  Brittle;  fracture  conchoidal. 

Hardness  =  7 ;  gravity  =2.6.  Waxy,  yellow,  red,  brown,  translu- 
cent to  opaque;  optically  biaxial,  thus  differing  from  quartz,  which  is 
uniaxial. 

Infusible;  insoluble. 

Ubiquitous. 

Opal 

Opal  differs  from  quartz  and  chalcedony  in  constitution,  since 
water  forms  a  part  of  its  molecule  (SiO2  and  H2O).  When  water 
occurs  in  quartz  it  is  mechanically,  not  chemically,  included  and  is 
given  off  with  a  cracking  noise  (decrepitation)  when  the  quartz  is 
heated  above  the  boiling-point  (100°  C.).  In  opal  it  is  chemically 
combined  in  definite  proportion,  constituting  most  commonly  about 
10  per  cent  of  the  mass.  At  the  moment  of  solidification  a  molecule 
of  silica  attracts  one  or  more  molecules  of  water,  called  the  water  of 
constitution,  in  distinction  to  mechanically  included  water.  It  is 
held  scarcely  more  firmly  than  are  the  different  molecules  which  con- 
stitute water  itself,  and  is  given  off  upon  heating  to  100°  C. 

Opal  differs  from  quartz  not  only  in  composition  but  in  physical 
characteristics  also.  It  lacks  crystal  form,  lines  cavities  with  layers 
which  on  their  free  sides  are  botryoidal,  reniform,  or  stalactitic,  is 
softer  and  lighter  than  quartz,  has  a  greasy  luster,  and  is  completely 
soluble  in  hot  potassium  hydrate. 

Of  the  several  varieties,  the  most  important  is  precious  opal 
(Nos.  3741  and  4725),  which  is  highly  prized  for  gems  in  spite  of  its 
opacity,  low  refraction,  and  moderate  hardness.  Its  beauty  depends 
upon  the  wonderful  play  of  colors  which  the  thin  films  composing  it 
cause  by  their  difference  in  refractive  index. 

For  centuries  near  Czerwenitza,  Hungary,  beautiful  yellow,  red, 
green,  and  blue  opals  have  been  found  disseminated  through  an 
altered  trachyte.  Similar  rock  near  Queretaro,  Mexico  (No.  3334), 
furnishes  a  fiery  red  opal  without  much  play  of  color,  the  so-called 
fire  opal.  Blue  and  green  opals  of  great  beauty  are  obtained  from 
nodules  of  brown  jaspery  limonite  in  Queensland  (No.  3741).  At  all 
these  localities  opals  of  various  other  shades  also  are  found. 


GUIDE  TO  MINERAL  COLLECTIONS 


A  perfectly  transparent  colorless  and  glassy  opal  found  in  botry- 
oidal  masses  is  called  hyalite.  Because  of  strain  due  to  the  solidi- 
fication of  the  original  jelly  mass,  it  often  shows  double  refraction. 
Siliceous  sinter  is  fibrous,  stalactitic,  porous,  or  powdery  opal  deposited 
by  hot  waters  in  Yellowstone  Park,  Iceland,  and  New  Zealand.  Its 
structure  is  influenced  by  the  algae  which  live  in  the  water,  just  as 
blades  of  grass  determine  the  form  of  ice  deposited  on  them  by 
winter's  rain.  The  shapes  of  the  sinter  or  geyserite  are  often  fantastic 
and  beautiful. 

SUMMARY 

Opal. — SiO2-H2O.     Amorphous;  brittle;  fracture  conchoidal. 
Hardness=6;  gravity  =  2.     Colorless,  white,  red,  brown,  yellow,  gre.en, 
blue.     Vitreous. 

Infusible;  yields  water;  soluble  in  potassium  hydrate. 
Hungary,  Bohemia,  Australia,  Mexico,  Idaho,  Montana. 

A.     THE  MONOXIDES 

Minerals  composed  of  an  equal  number  of  atoms  of  a  bivalent 
metal  and  of  oxygen  are  called  monoxides.  The  two  leading  examples 
are  cuprite  and  zincite. 

Cuprite 

Cuprite  (Cu2O),  or  "red  copper  ore,"  contains  the  largest  per 
cent  of  copper  (88.8  per  cent)  of  any  mineral  except  native  copper. 

It  occurs  in  well-formed  crystals 
which  exhibit  the  cube  (100), 
octahedron  (in),  dodecahedron 
(no),  trapezohedron  (211),  and 
trisoctahedron  (221).  A  typical 
crystal  is  shown  in  Figure  in. 
Granular  aggregates  and  dense 
masses  are  common.  Fresh  sur- 
faces of  cuprite  have  a  shining 
red  appearance  like  proustite,  but 
the  streak  is  brownish  red,  while 
FIG.  in.— Cuprite  that  of  proustite  is  scarlet.  Cu- 

prite  is   the  harder   of   the  two 

minerals.     It  is  found  in  mineral  veins  where  chalcocite  and  chalco- 
pyrite  have  been  subject  to  oxidizing  agencies.     Hence  many  veins 


loo 


V 


OXIDES  93 

which  above  the  water  line  contain  cuprite  are  composed  of  sul- 
phides, chalcocite,  chalcopyrite,  etc.,  below  that  line.  Cuprite  is  often 
coated  with  malachite,  a  green  copper  carbonate,  and  at  times  the 
change  extends  throughout  the  crystal  without  destroying  the  external 
form.  There  are  three  varieties  of  cuprite:  first,  the  ordinary  crys- 
tallized form  described  above;  second,  " chalcotrichite " — "plush 
copper  ore,"  consisting  of  slender  fibers  as  fine  as  a  hair,  elongated 
in  the  direction  of  a  cube  edge  or  a  cube  diagonal;  third,  "tile  ore,"  a 
brick-red,  earthy  mixture  of  cuprite  and  limonite. 

SUMMARY 

Cuprite. — Cu2O;  Cu  =  88.8per  cent,  O=n.  2  per  cent.  Regular  (in), 
(100),  (no);  brittle;  fracture  uneven. 

Hardness  =  3 .  5 ;  gravity  =  6.  Cochineal  red;  streak  brownish-red. 
Metallic,  adamantine ;  translucent;  refraction  very  strong,  00  =  2.85. 

Fusible;  soluble  in  strong  hydrochloric  acid. 

In  Cordilleran  states  hydrochloric  acid. 

Zincite 

In  Sussex  County,  New  Jersey,  zincite  (ZnO)  occurs  in  quantities 
sufficient  to  make  it  a  profitable  source  of  zinc  (Nos.  314,  315,  524, 
747).  It  is  of  brownish  or  deep  red  color, 
and  has  a  characteristic  orange-yellow 
streak.  It  is  usually  massive,  but  when 
crystals  are  found  they  are  in  the  hex- 
agonal system  and  "  hemimorphic "  or 
"polar,"  since  their  planes  are  not  sym- 
metrically arranged  around  the  center 
(Fig.  112).  Some  specimens  of  zincite 
contain  as  much  as  7  per  cent  of  man- 
ganese oxide  (MnO),  which  is  present  in 

solid  solution  as  an  isomorphous  mixture. 

r^,,     ....  ,.j       ,-    .        .  FIG.  112. — Zincite 

That  it  is  a  solid  solution  is  suggested  by 

the  fact  that  with  increase  of  the  amount  of  manganese  the  mineral 
becomes  more  yellow. 

SUMMARY 

Zincite. — ZnO;  Zn  =  8o/3  per  cent,  0=19.7  per  cent.  Hexagonal. 
Symmetry,  dihexagonal  polar.  Cleavage,  perfect  (oooi),  (1010).  Brittle; 
fracture  subconchoidal. 


94  GUIDE  TO  MINERAL  COLLECTIONS 

Hardness  =  4;    gravity  =5. 6.     Blood  red,  streak  orange;    luster,  sub- 
adamantine;  translucent;  double  refraction  positive. 
Infusible;  soluble  in  hydrochloric  acid. 
New  Jersey. 

B.    THE  SESQUIOXIDES 

Minerals  having  three  atoms  of  oxygen  to  two  of  another  element, 
usually  a  metal,  are  called  sesquioxides.  As  examples  we  select  co- 
rundum and  hematite. 

Corundum 

Since  very  early  in  human  history  corundum  (A12O3)  has  been 
recognized  and  used  by  man.  The  words  sapphire  and  ruby  occur  in 
literature  two  thousand  years  old.  Sapphire  is  blue  corundum  and 
ruby  the  red  variety.  Ordinary  corundum,  being  non-transparent 
and  unattractive  in  color,  did  not  early  arrest  attention.  When 
cleaved,  its  fragments  resemble  feldspar,  one  of  the  most  abundant 
of  minerals,  and  hence  would  not  be  easily  recognized.  Though  the 
name  corundum  is  an  old  Hindu  word,  the  mineral  was  first  brought 

from  China  to  Europe,  and  was  first 
OOO1  analyzed  by  a  German,  Klaproth, 

in  1787. 

A  third  variety  of  corundum, 
emery,  is  granular  and  dark  in 
color  because  mixed  with  iron 
oxides  such  as  magnetite.  The 
name  "emery"  is  of  Greek  origin, 
and  some  of  the  isles  of  Greece, 
especially  Naxos,  were  long  the 
FIG.  113.— Corundum  chief  source.  The  ancient  lapi- 

daries  used   it   for    grinding    and 

polishing,  and  today  its  use  is  very  extensive,  although  pure  corun- 
dum is  preferable,  being  superior  to  emery  in  hardness. 

Sapphire,  ruby,  ordinary  corundum,  and  emery  differ  only  in 
purity  of  chemical  composition,  color,  and  in  structure.  Emery  is 
the  least  pure,  is  opaque,  and  occurs  only  in  grains.  Corundum  and 
the  transparent  varieties  crystallize  in  good  hexagonal  crystals  of 
rhombohedral  symmetry  (calcite  class)..  While  the  sapphire  and 
ruby  are  rare,  corundum  is  abundant  and  may  best  be  taken  as  the 
representative  of  the  species.  Figure  113  shows  a  common  and  typical 


OXIDES 


95 


form.  It  is  composed  of  a  rhombohedron  truncated  with  a  basal 
plane.  In  such  a  crystal  it  is  evident  that  there  are  three  planes  of 
symmetry  intersecting  in  the  c  axis,  and  that  if  the  mineral  were 
revolved  around  this  axis  the  planes  would  repeat  themselves  three 
times  during  a  complete  revolution.  Thus  the  c  axis  is  an  axis  of 
trigonal  symmetry.  The  three  horizontal  axes  are  axes  of  binary 
symmetry. 

More  common  than  the  simple  crystals  are  those  composed  of 
rhombohedrons  R  (idi),  dihexagonal  pyramids  (2423),  diagonal 
prisms  (1120),  and  base  (0061)  (Fig.  114). 

Repetition  of  dihexagonal  pyramid  planes  of  different  inclination 
to  the  c  axis  produces  undulating  prisms  and  rounded  crystals.  Often 


422 


FIG.  114. — Corundum 


FIG.  115. — Corundum  with  twinning 
lamellae  parallel  to  R. 


twinning  lamellae  parallel  to  the  rhombohedron  (ion)  cause  stria- 
tions  on  the  basal  plane  and  divide  the  crystal  into  sextants 
(Fig.  115).  When  the  basal  plane  is  polished,  these  striations  reflect 
the  light  in  such  a  manner  as  to  produce  a  beautiful  six-rayed  star 
("asterism"). 

The  largest  amount  of  corundum  has  been  found  as  water- worn 
pebbles,  which,  though  rounded,  usually  retain  their  crystal  shape 
because  of  their  great  hardness.  Coarse  pieces  and  granular  masses 
intergrown  with  mica  are  also  characteristic.  In  the  Boston  Society 
Natural  History  Museum  is  a  group  of  large  corundum  crystals 
weighing  several  hundred  pounds. 

True  cleavage  is  wanting,  but  there  is  a  lamellar  separation 
parallel  to  R  and  the  base,  due  to  layers  of  twin  crystals. 


96  GUIDE  TO  MINERAL  COLLECTIONS 

Vitreous  luster  is  characteristic.  Few  minerals  have  as  great 
variety  of  color.  Colorless  examples  are  rare.  When  the  trans- 
parent or  translucent  varieties  are  red,  they  are  called  ruby.  If  of 
the  shade  known  as  "pigeon  blood,"  they  are  more  highly  prized 
than  any  other  gem.  When  deep  blue  to  lilac  in  color,  they  are 
called  sapphire;  yellow  to  brown,  oriental  topaz;  green,  oriental 
emerald;  purple,  oriental  amethyst — a  good  example  of  the  common 
tendency  to  call  one  object  by  the  name  of  another  in  order  to  enhance 
its  value — a  tendency  which  should  be  resisted.  The  color  is  due  to 
oxides  of  iron  or  chromium.  Sapphire  exposed  to  action  of  radium 
bromide  assumes  successively  green,  light-yellow,  and  dark-yellow 
tints,  while  ruby  develops  in  succession  shades  of  violet,  blue,  green, 
and  yellow.  They  regain  their  original  color  upon  heating. 


W 


FIG.    116. — Cross-section   of   dichro-          FIG.  117. — Direction  of  vibration  of 
scope.  two  rays  of  light  passing  through  calcite 

prism. 

In  corundum  (as  in  other  transparent  minerals  not  belonging  to 
the  regular  system)  the  color  depends  upon  the  direction  in  which 
light  passes  through  the  crystal.  Hence  false  gems  can  be  readily 
separated  from  genuine  ones.  The  mineral  needs  only  to  be  examined 
through  a  dichroscope  (S«,  "two,"  xP^Ma,  " color")  (Fig.  116),  an 
instrument  consisting  of  a  metal  tube  three  inches  long  fitted  with 
a  weak  lens  at  the  end  a  to  be  held  to  the  eye  and  having  a  small 
square  opening  at  the  end  b  against  which  the  mineral  to  be  examined 
is  held.  In  the  tube  is  a  cleavage  rhomb  c  of  calcite  (CaCO3),  a 
transparent  mineral  which  has  the  power  of  dividing  a  ray  of  entering 
light  into  two  rays  that  vibrate  in  planes  at  right  angles  to  each  other 
and  consequently  make  a  single  point  appear  double  (Plate  XXI). 
Such  a  thickness  of  calcite  is  chosen  as  to  make  the  square  opening 
appear  like  two  openings  side  by  side.  The  transmitted  light  vibrates 
in  the  direction  indicated  by  the  arrows  in  Figure  117.  One  ray  of 
light  is  called  the  ordinary  (co)  and  the  other  the  extraordinary  (e). 


OXIDES  97 

When  a  piece  of  colored  glass  is  placed  on  the  square  opening,  both 
images  have  the  same  color.  If  a  ruby  is  placed  on  the  opening,  the 
ordinary  ray  (co)  looks  deep  red,  while  the  extraordinary  (e)  is  violet 
red.  A  sapphire  appears  deep  blue  for  the  ordinary  ray  («)  and 
greenish  blue  for  the  extraordinary  (e)  (Figs.  118  and  119). 

Rubies  and  sapphires  are  found  in  granite,  basalt,  gneiss,  mica 
and  chlorite  schist,  granular  limestone  and  dolomite,  and  in  gravels 
derived  from  them.  The  finest  sapphires  have  been  obtained  in 
Ceylon,  the  most  valuable  rubies  in  Burma.  Montana  and  North 
Carolina  furnish  valuable  sapphires,  rubies,  corundum,  and  emery. 


D 


FIG.  1 1 8. — Ruby  FIG.  119. — Sapphire 

The  examples  shown  come  from  widely  distributed  localities: 
rubies  from  Burma  (No.  3339),  sapphires  from  Kashmir  (No.  3341) 
and  from  Queensland  (No.  3340),  corundum  from  North  Carolina 
(No.  3342)  and  New  Jersey  (Nos.  506  and  519),  emery  from  Massa- 
chusetts (No.  1254). 

SUMMARY 

Corundum. — A12O3;  Al=  52 . 9  per  cent,  0  =  47 .  i  per  cent.  Hexagonal, 
symmetry  rhombohedral  (calcite  class).  0:^=1:1.363.  R  (ion),  (2423), 
(1120).  Parting  or  pseudo-cleavage ;  brittle;  fracture  conchoidal. 

Hardness=g;  gravity =4.  Many  colors,  vitreous,  transparent, 
dichroic,  refraction  strong,  00=1.768.  Double  refraction,  negative  weak. 
o>  —  e  =  o.oo8. 

Infusible;  insoluble. 

North  Carolina,  Montana,  Idaho,  India. 

Hematite 

Of  all  minerals  in  the  mineral  kingdom,  none  is  more  important 
from  a  human  standpoint  than  hematite  (Fe2O3),  inasmuch  as  it  is 
the  mineral  which  furnishes  the  greatest  quantity  of  iron — a  metal 
upon  which  modern  civilization  is  founded  and  which  may  be  said  to 
furnish  a  standard  of  development  of  a  people. 


98 


GUIDE  TO  MINERAL  COLLECTIONS 


In  appearance  hematite  varies  greatly  with  its  physical  condition. 
When  well  crystallized  it  is  metallic,  black,  6 . 5  in  hardness  and  5  in 
specific  gravity.  When  earthy  and  friable  it  is  submetallic,  red,  soft, 
and  of  low  specific  gravity. 

Hematite  is  isomorphous  with  corundum,  that  is,  it  has  the  identi- 
cal shape,  though  it  is  a  different  chemical  substance.  The  best 
crystals  are  found  in  igneous  rocks.  The  island  of  Elba  has  for 
many  years  furnished  beautiful  crystals  which  show  the  same  rhombo- 
hedral  symmetry  already  studied  in  corundum. 

The  rhombohedron  R  (1011)  occurs  alone  (Fig.  120)  or  combined 
with  a  negative  flat  rhombohedron  —%R  (0112).  Rounded  crystals 

(Fig.  121)  composed  of  a  flat 
rhombohedron  %R  (1014),  the 
ordinary  rhombohedron  R 
(1011),  and  the  bipyramid 
(2243)  are  characteristic.  Tabu- 
lar crystals  composed  of  a  broad 
basal  plane  (oooi),  truncating 
short  rhombohedrons  R  (1011), 
and  secondary  prism  planes 
(1120)  often  twinned  parallel 
to  a  prism  plane  are  common 
(Fig.  122).  They  are  often  so 
grouped  as  to  form  rosettes, 

"iron  roses." 
FIG.   120. — Model  of  a  rhombohedron  _    ..    .  .      .  .      ... 

(101 1)  =R  Individual  crystals  of  minute 

size  occurring  in  myriads  some- 
times constitute  great  masses  of  ore  and  form  the  variety  called  mica- 
ceous hematite.  The  fine  scales  of  this  variety  of  hematite  are  usually 
imperfectly  cemented  so  that  they  easily  rub  off  and  give  a  false 
impression  of  the  hardness  of  the  mineral. 

When  heated  in  a  reducing  flame,  the  mineral  loses  its  red  color 
and  becomes  magnetic  but  does  not  melt.  The  electrical  con- 
ductivity of  hematite  has  been  accurately  measured  and  is  found 
to  be  two  times  as  great  in  the  vertical  as  in  the  horizontal  direc- 
tion of  the  crystal.  Hematite  is  one  of  nature's  most  universal 
paints.  It  colors  the  rocks  red  and  brown  and  yellow  as  it  varies  in 
amount  and  in  its  degree  of  oxidation.  About  6  per  cent  of  the 


PLATE  XIX 


Botryoidal  hematite,  Cumberland,  England 


,  Limonite.  Hardin  County,  Illinois 


OXIDES  99 

earth's  crust  is  iron  and  a  large  part  of  iron  is  in  the  form  of 
hematite.  Illinois  has  no  workable  deposits,  but  the  mineral  occurs 
in  flakes,  incrustations,  or  red  ochreous  balls,  or  as  coloring  matter  in 
all  parts  of  the  state  and  in  massive  micaceous  or  compact  pieces 
in  the  drift. 

In  many  parts  of  the  world  granular  hematite  (No.  1581)  forms 
such  extensive  deposits  as  to  furnish  the  largest  source  of  iron.  Well- 
crystallized  lustrous  hematite  is  capable  of  receiving  a  high  polish  and 
reflects  the  light  as  does  a  looking-glass,  and  hence  has  been  called 
"  specularite "  (Nos.  3894  and  3895).  The  fibrous  and  columnar 
varieties  are  composed  of  individual  threads  or  pencils  more  or  less 
parallel  and  ending  in  rounded  grapelike  (botryoidal)  (No.  3343)  or 


1011 

__  11ZO 

2245 

FIG.  121. — Hematite  FIG.  122. — Tabular  hematite  crystal 

twinned  parallel  to  the  prism. 

kidney-shaped  (reniform)  surfaces  and  exhibiting  curvilamillar  mark- 
ings in  various  places  (No.  3345).  Botryoidal  masses  break  up  into 
conical  forms  known  as  "  pencil  ore."  Masses  that  are  earthy  and 
soft  enough  to  adhere  to  the  fingers  like  graphite,  and  usually  bright 
red  in  color,  suggested  a  name  for  the  mineral  (hematite,  "blood- 
stone") to  Theophrastus  three  hundred  years  before  Christ  (Nos.  343, 
608,  and  4496).  Thin  flakes  such  as  may  be  seen  in  microscopic 
slides  appear  blood  red  in  transmitted  light,  just  as  the  powder  does 
in  ordinary  light. 

The  great  deposits  of  hematite  in  Michigan,  Minnesota,  Wis- 
consin, and  Alabama  make  it  possible  for  the  United  States  to  lead 
the  world  in  the  production  of  iron. 


100 


GUIDE  TO  MINERAL  COLLECTIONS 


SUMMARY 

Hematite. — Fe2O3 ;  Fe  =  70  per  cent,  O  =  30  per  cent.  Hexagonal ;  sym- 
metry dihexagonal,  alternating  (calcite  class).  a:c=  1.3656.  R  (ion), 
—  $R  (0112),  %R  (1014),  (1120),  (2243),  (oooi).  Cleavage  (parting) 
parallel  R  and  (oooi)  imperfect;  brittle;  fracture  uneven. 

Hardness  =  6 ;  gravity  =  5.2.  Iron  black  to  blood  red ;  streak  brownish 
red  or  purple;  metallic;  in  thinnest  pieces  translucent  and  red. 

Infusible  alone  before  blowpipe;  powder  difficultly  soluble  in  concen- 
trated hydrochloric  acid. 

Elba,  Switzerland,  New  York  to  Alabama,  Minnesota,  Wisconsin, 
and  Missouri. 

C.    HYDRATED  SESQUIOXIDES 
Three  minerals  may  be  chosen  to  represent  this  group.     They  are: 

Manganite  Mn2O3  •  H2O 

Goethite  Fe2O3-H2O 

Limonite  2  Fe2O3  •  3H2O 

Manganite 

From  a  mineralogical  point  of  view  manganite  (Mn2O3-H2O)  is  of 
more  importance  than  pyrolusite,  though  not  so  commercially,  since 

,O01  JOO 


101 


FIG.  123. — Manganite 


FIG.    124. — Manganite  twinned  par- 
allel to  (011). 


pyrolusite  and  another  manganese  oxide,  psilomelane,  are  mined  in 
great  quantities,  while  manganite  is  comparatively  rare.  Manganite 
is  well  denned  in  its  physical  and  chemical  characteristics.  It 
occurs  in  steel  gray  to  black,  moderately  hard  (hardness,  4),  ortho- 
rhombic  prisms,  which  are  usually  grouped  in  bundles  and  striated 
vertically.  The  prisms  end  in  basal  planes  and  are  striated  hori- 


OXIDES 


zontally  (Fig.  123).  The  customary  planes  are  (210),  (no),  (120), 
(oio),  (in),  (101),  (on),  and  (021).  Twins  parallel  to  (on)  are 
common  (Fig.  124).  Fibrous,  radiated,  and  granular  forms  are  rep- 
resentative (No.  3356). 

Manganite  is  formed  by  deposition  of  manganese  oxide  in  many 
springs  and  often  replaces  other  minerals,  assuming  their  forms,  i.e., 
becoming  a  pseudomorph.  For  example,  at  Ilfeld,  Germany,  man- 
ganite  (No.  3357)  replaces  calcite,  and  since  the  calcite  has  been 
deposited  from  an  aqueous  solution  it  is  natural  to  conclude  that 
manganite  has  a  like  origin.  On  the  other  hand,  manganite  changes 
into  pyrolusite  by  loss  of  water.  The  process  which  occurs  in  nature 
is  imitated  by  slow  heating  of  manganite  with  free  access  of  air. 
Pyrolusite  is  often  found  with  a  manganite  core,  showing  that  the 
process  is  but  partially  completed. 

SUMMARY 

Manganite.  —  Mn2O3-H2O;  Mn2O3  =  89.7  per  cent,  H2O=io.3  per 
cent.  Orthorhombic.  a:6:c  =  0.844  :  i  :  o.  545  ;  (ooi),  (in),  (on), 
(101),  (no),  (oio),  (210),  (120),  (021);  twinning  parallel  (on);  cleavage 
parallel  (oio)  perfect;  brittle;  fracture  uneven. 

Hardness  =  4;  gravity  =  4.  4.  Steel  gray;  streak  reddish  black;  sub- 
metallic;  opaque. 

Infusible;  soluble  in  hydrochloric  acid  with  evolution  of  chlorine. 

Hartz  Mountains,  Michigan,  Colorado. 

Goethite 

Goethite  (Fe2O3'H2O),  named  in  honor  of  the  poet  Goethe,  who 
was  interested  in  mineralogy  as  well  as  in  other  natural  sciences,  is  an 
iron  hydrate  occurring  in  lustrous  brown  or  black  orthorhombic 
prisms  terminated  with  pyramids  (No.  547). 

The  usual  planes  (Fig.  125)  are  (no),  (210),  (oio),  (in),  '(on), 
and  rarely  (ooi).  Prism  planes  are  often  striated.  Columnar  forms 
and  capillary  crystals  radially  grouped  are  common.  The  last  are 
called  "  needle  iron  stone."  Columnar  and  capillary  crystals  bunched 
together  in  radiated  and  concentric  masses  which  end  in  rounded  sur- 
faces are  said  to  be  "reniform."  Goethite  also  occurs  in  thin  red 
scales  composed  of  (100),  (oio),  (401),  (on)  (Fig.  116).  Multitudes 
of  these  fine  scales  attached  on  one  side  produce  a  mass  with  velvety 
luster.  Because  of  their  color  they  are  called  "ruby  mica,"  and  in 


&UIIDE  TO  MINERAL  COLLECTIONS 


the  finest  scales  are  transparent,  reddish  yellow,  and  under  the  micro- 
scope dichroic,  i.e.,  exhibit  two  different  colors  when  the  light  travers- 
ing them  is  allowed  to  vibrate  first  in  one  and  then  in  another  direction 
through  a  dichroscope  (see  p.  96).  Thus  are  they  easily  distin- 
guished from  scales  of  hematite,  which  are  monochroic.  Goethite 
crystals  are  common  alteration  products  in  secondary  cavities,  and 
give  rise  to  a  bronze  sheen  and  opalescent  tint.  When  goethite  is 
heated  it  gives  off  water,  becomes  red,  and  changes  to  hematite. 


210 


--O1O 


FIG.  125. — Goethite 


401 
100 


FIG.  126.— Goethite 


Further  heating  with  some  reducing  agent  makes  it  black  and  mag- 
netic, and  heating  continued  until  all  the  oxygen  is  removed  produces 
pure  iron.  Goethite  is  much  less  abundant  than  either  hematite  or 
magnetite,  but  is  a  common  associate  of  these  and  other  iron  ores  in 
veins.  Bohemia,  Cornwall,  Connecticut,  the  Lake  Superior  region, 
and  Colorado  yield  the  best  crystals. 


SUMMARY 

Goethite.— Fe2O3'H2O;  Fe203  =  89-9  per  cent,  H2O  =  io.i  per  cent. 
Orthorhombic.  a:b:c  =  o. 913: 1:0.607;  (no),  (210),  (on),  (in),  (ooi), 
(401),  (oio),  (100).  Cleavage  parallel  (oio)  perfect;  brittle;  fracture 
uneven. 

Hardness=5;  gravity =4.  Brown  to  black;  translucent;  double 
refraction  positive;  dichroic. 

Fusible  with  difficulty  to  magnetic  bead;  soluble  in  hydrochloric 
acid. 

Bohemia,  Cornwall,  Connecticut,  Michigan,  Colorado. 


OXIDES  103 

Limonite 

Much  more  common  than  goethite  is  the  fibrous,  dense,  or  earthy 
iron  hydrate,  limonite  (2Fe2O3'3H2O)  named  from  \einuv,  the 
Greek  for  a  moist  grassy  place,  since  it  is  found  as  a  brownish-yellow 
deposit  in  bogs.  It  causes  the  iridescent  slime  seen  in  sluggish 
streams  and  pools,  replacing  the  decaying  vegetable  matter.  The 
rusting  of  iron  is  simply  a  change  to  limonite.  There  are  several 
varieties  founded  upon  form,  origin,  and  condition  of  the  mineral  in 
deposits.  First,  there  is  the  fibrous,  radial,  curvilaminar  limonite, 
often  with  black  glazed  (No.  1881)  or  opalescent  lustrous  surface 
(No.  3359),  lining  cavities  and  geodes,  and  hanging  in  stalactites  in 
caves  (Nos.  2571  and  244);  second,  dense  compact  limonite  (No.  298), 
in  veins  where  it  has  been  deposited  by  circulating  waters  which  have 
gathered  it  from  the  surrounding  decomposing  rocks;  third,  extensive 
beds  formed  by  waters  circulating  above  ground  and  emptying  into 
ponds.  These  beds  are  often  oolitic  (No.  1747),  i.e.,  composed  of 
myriads  of  small  grains,  among  which  are  found  fragments  of  algae, 
foraminifera,  bryozoans,  etc.  Such  deposits  are  analogous  to  the 
fourth  variety — bog  iron  ore,  forming  today  in  swamps  and  making 
granular,  nodular,  concretionary,  earthy,  or  sandy  masses.  On  the 
bottom  of  many  lakes  is  a  black  mud  from  which  small  grains  of 
limonite  are  separating.  Measurements  made  in  Sweden  show  that 
deposits  six  inches  thick  have  been  formed  in  twenty  years.  The 
fifth  variety  consists  of  grains  as  large  as  a  pea  (pisolitic).  The 
grains  often  show  concentric  structure  and  fill  clefts  in  limestone  and 
are  cemented  together  in  clumps.  Sixth,  constantly  associated  with 
the  denser  limonite  and  other  iron  ores  is  a  yellowish-brown,  soft, 
porous  mass  called  yellow  ochre.  It  is  porous  because  it  is  a  rem- 
nant left  after  the  dissolution  of  other  materials. 

That  limonite  is  a  secondary  mineral  derived  from  such  minerals 
as  siderite  and  also  from  pyrite,  hematite,  and  magnetite,  is  evident 
because  the  form  of  the  original  crystal  is  often  retained — the  rhombo- 
hedrons  of  siderite,  cubes  of  pyrite,  octahedrons  of  magnetite,  and 
hexagonal  plates  of  hematite.  Different  stages  of  the  process  show 
different  proportions  of  the  original  crystals  still  unaffected.  All  the 
steps  of  the  transition  from  original  to  derived  material  can  be  traced. 

The  brown  streak  of  limonite,  its  inferior  hardness  and  weight, 
and  the  presence  of  water  distinguish  it  from  hematite.  It  is 


104  GUIDE  TO  MINERAL  COLLECTIONS 

harder  and  lighter  than  the  crystallized  goethite  and  contains  more 
water. 

Because  of  the  ease  with  which  limonite  fuses,  it  was  probably 
the  first  mineral  to  be  used  by  man  as  a  source  of  iron. 

SUMMARY 

Limonite. — 2Fe2O3«3H2O;  Fe2O3  =  88.5  per  cent,  H20=i4-S  per  cent. 
Amorphous,  fibrous,  concentric,  dense,  earthy. 

Hardness  =5. 5;  gravity  =  3. 8.  Dark  brown;  streak  yellow  brown; 
submetallic;  opaque. 

Fusible  to  magnetic  bead ;  soluble  in  hydrochloric  acid. 

Scotland,  Sweden,  Connecticut,  New  York,  Pennsylvania,  Alabama, 
Ohio,  Illinois. 

D.     ALUMINITES,  FERRITES,  MANGANITES,  CHROMITES 

The  chief  minerals  of  this  group,  all  of  which  crystallize  in  the 
regular  system  with  the  octahedron  as  a  common  form,  are 

Spinel  MgO-Al2O3 

Manganit  e  FeO  •  Fe2O3 

Franklinite  (Fe,Zn,Mn)O-  (Fe,Mn)2O3 

Chromite  FeO-Cr2O3 

Spinel. 

Spinel  is  a  mineral  useful  as  a  gem  because  of  its  beauty  and  hard- 
ness. The  minute  quantities  of  various  elements  which  replace  a 
part  of  the  Mg  or  Al  in  the  typical  formula  MgO  •  A12O3  produce  differ- 
ent colors.  For  example,  the  dark  green  to  black  opaque  spinel 
(ceylonite)  contains  Fe.  The  yellowish-  or  greenish-brown  variety 
(picotite)  contains  Fe  and  Cr,  and  the  grass-green  variety  (chlor- 
spinel)  contains  Fe  and  Cu.  But  the  typical  spinel  approaching 
most  nearly  the  formula  MgO*Al2O3  is  of  a  beautiful  clear  red  color, 
generally  transparent,  and  called  precious  spinel.  The  purest  red  is 
called  ruby  spinel;  the  orange  red,  rubicelle;  and  the  violet,  the 
almandine  spinel. 

From  earliest  times  precious  spinel  was  prized  as  a  gem,  but  was 
not  distinguished  from  ruby  until  Rome  de  ITsle  studied  it  (1783), 
though  these  minerals  differ  in  crystal  form,  cleavage,  optical  proper- 
ties, hardness,  and  density.  The  specific  gravity  of  spinel  is  3.5, 
while  that  of  ruby  is  4;  spinel  is  only  8  in  hardness,  while  ruby  is  9. 


OXIDES 


105 


Spinel  shows  no  pleochroism  and  is  iso tropic,  i.e.,  it  allows  the  light 
to  pass  through  it  similarly  in  all  directions,  as  would  be  expected  of 
a  mineral  crystallizing  in  the  regular  system. 

In  gem-bearing  sands  of  Ceylon,  Burma,  and  Siam,  which  have 
long  been  the  source  of  precious  spinel,  are  found  small,  sharp-edged 
octahedrons  and  typical  spinel  twins,  where  the  octahedral  face  is 
the  twinning  plane  (Fig.  127).  The  corners  of  the  octahedrons  are 


FIG.  127. — Spinel  twin 


FIG.  128.— Spinel 


often  beveled  by  trapezohedrons  and  the  edges  by  dodecahedrons, 
giving  the  crystal  a  rounded  appearance.  Dark-colored  varieties 
occur  in  abundance  at  Vesuvius,  in  New  York,  New  Jersey,  and 
North  Carolina. 

SUMMARY 

Spinel. — MgO-Al2O3;  MgO=28.2  per  cent,  Al2O3  =  7i.9  per  cent. 
Regular;  holosymmetric;  (in)..  Cleavage  imperfect  parallel  (in); 
brittle;  fracture  conchoidal. 

Hardness  =  6;  gravity =3. 5.  Red,  yellow,  green,  black;  streak  white; 
luster  vitreous;  transparent;  refraction  high,'w  =  1.715. 

Infusible;  soluble  with  difficulty  in  sulphuric  acid. 

Burma,  Ceylon,  Appalachian  region. 

Magnetite 

The  third  mineral  in  importance  as  a  source  of  iron  is  magnetite, 
which  derived  its  name,  according  to  Pliny,  from  the  shepherd  Magnes, 
who  found  his  iron-pointed  staff  attracted  by  the  mineral  while  he 
was  wandering  over  Mount  Ida.  It  is  the  most  magnetic  of  all 


io6 


GUIDE  TO  MINERAL  COLLECTIONS 


FIG.  129. — Magnetite 


minerals,  sometimes  possessing  polarity  and  attracting  particles  of 
iron  to  itself  (loadstone)  (No.  334).  Usually  it  is  simply  itself 
attracted  by  a  magnet.  Because  of  its  magnetism  it  is  easily  sepa- 
rated from  the  sands  of  the  ocean  or  lake  or 
the  streams,  in  which  it  is  found  in  abun- 
dance. In  various  sedimentary  deposits 
in  igneous  and  in  metamorphic  rocks  it 
occurs  as  grains,  granules,  and  masses. 

Crystals  of  magnetite  show  most  com- 
monly octahedral  (No.  3346)  and  dodeca- 
hedral  forms  in  which  the  dodecahedron  is 
striated  parallel  to  the  octahedral  edges 
(No.  548),  because  of  oscillatory  combina- 
tion (Fig.  129).  The  magnetism  and  the  black  streak  of  magnetite 
distinguish  it  from  hematite. 

SUMMARY 

Magnetite. — FeO  •  Fe2O3 ;  FeO  =  3 1  per  cent ;  Fe2O3  =  69  per  cent.     Regu- 
lar; holosymmetric;  (in),  parting,  parallel  (in);  brittle;  fracture  uneven. 
Hardness  =  6;  gravity  =5. 8.     Black;  streak  black;  metallic;  opaque. 
Magnetic,  sometimes  polar. 

Fusible  with  difficulty;  powder  easily  soluble  in  hydrochloric  acid. 
Scandinavia,  Urals,  Altai  Mountains,  New  York,  Pennsylvania,  New 
Mexico,  North  Carolina. 

Franklinite 

Franklinite  closely  resembles  magnetite  in  form,  color,  hardness, 
and  weight,  but  has  a  browner  streak,  is  more  commonly  rounded  on 
its  octahedral  edges,  and  is  but  slightly  magnetic.  Its  usual  associa- 
tion with  the  red  zinc  oxide  (No.  3348),  zincite,  renders  its  determina- 
tion by  physical  means  less  difficult,  but  chemical  test  (search  for  a 
zinc  incrustation  on  charcoal  or  the  amethystine  color  of  manganese 
in  the  borax  bead)  is  necessary  for  its  accurate  determination. 

The  mineral  receives  its  name  from  Franklin  Furnace,  New 
Jersey,  where  it  has  been  found  in  great  quantities. 

SUMMARY 

Franklinite. — (Fe,Zn,Mn)O.(Fe,Mn)2O3.  Regular;  holosymmetric; 
(111);  rounded  grains.  Resembles  magnetite  in  physical  properties,  but  is 
slightly  magnetic  and  browner  in  streak. 


OXIDES  107 

Hardness  =  6 ;  gravity  =  5. 

Infusible,  soluble  in  hydrochloric  acid. 

Franklin  Furnace,  New  Jersey. 

Chromite 

Chromite  resembles  magnetite  and  franklinite  in  form  and 
color  (No.  543),  but  is  slightly  softer  (hardness  5.3)  and  lighter 
(gravity,  4.5).  The  best. means  of  identifying  it  is  to  test  for  the 
green  color  which  it  gives  to  a  cold  borax  bead. 

Chromite  owes  its  importance  to  the  fact  that  it  furnishes  prac- 
tically all  the  chromium  used  in  the  arts  and  manufactures.  Chro- 
mium compounds  are  used  to  color  porcelains  and  enamels  green,  and 
to  dye  calicoes,  etc.  Their  most  important  use  of  late  years,  however, 
has  been  to  harden  steel.  Before  the  world-war  nearly  a  million  dollars' 
worth  of  chromite  was  imported  annually,  a  few  thousand  dollars'  worth 
only  being  produced  in  this  country.  As  a  result  of  government  inves- 
tigation and  encouragement  production  of  domestic  chromite  was 
greatly  increased.  It  is  found  in  rocks  consisting  chiefly  of  olivine 
and  serpentine. 

SUMMARY 

Chromite. — FeO  •  Cr2O3 ;  FeO  =  32  per  cent,  Cr203  =  68  per  cent.  Regu- 
lar; holosymmetric  (in);  granular,  massive;  uneven;  fracture  brittle. 

Hardness  =5. 5;  gravity  =  4. 5.  Black,  yellowish  red  in  very  thin 
sections;  dark  brown. 

Infusible;  insoluble  in  acids,  decomposing •  when  fused  with  sodium 
sulphate. 

New  Caledonia,  Bohemia. 

E.    DIOXIDES 

The  minerals  in  this  group  contain  two  atoms  of  oxygen  to  one 
of  the  basic  element.  Those  which  most  merit  attention  are : 

Cassiterite  SnO2 

Rutile  TiO2   ' 

Pyrolusite  Mn02 

Cassiterite 

This  mineral,  the  only  important  source  of  tin,  has  been  known 
since  earliest  times  and  was  used  by  the  ancients  to  make  bronze. 
In  color  it  is  usually  dark  brown  or  black.  It  is  hard  (hardness,  6.5), 


io8 


GUIDE  TO  MINERAL  COLLECTIONS 


heavy  (gravity,  7),  insoluble,  and  infusible,  and  is  usually  in  the  form 
of  rounded  grains  and  pebbles  or  short  stout  crystals. 

The  color  of  cassiterite  depends  upon  impurities  such  as  iron 
oxide  (Fe2O3),  tantalum  oxide  (Ta2Os),  etc.  Pure  varieties,  which 
are  rare,  are  colorless,  transparent,  and  lustrous,  and,  were  they  a 
little  harder,  would  be  much  prized  for  gems.  In  Mexico  yellowish 
varieties  are  found,  and  Australia  has  yielded  some  fine  red  speci- 
mens; but  most  cassiterite  is  black. 

Owing  to  its  hardness,  weight,  and  stability,  it  occurs  in  stream 
deposits  as  "stream- tin"  and  has  been  successfully  mined  in  the 
Malay  Peninsula,  Australia,  the  Black  Hills,  and  California.  In 
primary  deposits  it  is  persistently  associated  with  certain  acidic 


101 


101 


JIO 


010 


FIG.  130. — Cassiterite 


lit" 

FiG.  131. — Cassiterite  twinned  on  (oil) 


igneous  rocks,  such  as  granites  and  pigmatites,  where  it  has  crystallized 
in  short,  stout  tetragonal  crystals,  usually  twinned.  Simple  crystals 
(Fig.  130)  composed  of  (m),  (no),  (100),  (101)  are  rarer  than  the 
twin  forms  which  are  so  characteristic.  The  twinning  plane  is 
parallel  (on),  as  shown  in  Figure  131.  Prism  planes  are  usually 
striated  parallel  to  c.  Basal  planes  are  almost  unknown.  Slender 
prisms,  having  acute,  di tetragonal  pyramids  such  as  (321)  in  addition 
to  the  more  usual  pyramids,  occur  rarely  and  are  called  " needle  tin." 
Some  of  the  massive  varieties  have  a  radiated  fibrous  structure,  are 
arranged  in  curvilaminar  layers  of  different  shades,  and  in  a  botryoidal 
surface  lack  the  luster  of  the  ordinary  crystal.  Being  remarkably 
dull  and  wooden,  they  are  called  "wood  tin."  Little  brown-banded 
spherical  nodules  with  the  same  fibrous  structure  are  called  "toad's 


OXIDES 


109 


eye  tin"  in  Cornwall,  which  has  long  been  the  most  productive  tin 
region. 

The  minerals  associated  with  cassiterite  suggest  its  origin.  They 
are  commonly  apatite,  fluorite,  zinnwaldite,  topaz,  and  tourmaline  —  all 
of  which  contain  fluorine  and  lead  to  the  thought  that  vapors  contain- 
ing fluorine  were  influential  in  the  deposition  of  cassiterite.  Daubree 
produced  cassiterite  artificially  by  the  action  of  steam  on  tin  fluoride. 
But  cassiterite  is  produced  in  two  other  ways  also.  Violet-colored 
simple  crystals  have  been  made  in  tin  works  by  the  oxidation  of 
metallic  tin,  and  cassiterite  has  been  found  replacing  organic  remains 
and  cementing  nodules,  as  would  be  the  case  were  it  deposited  from 
solution,  or  from  vapors. 

The  chief  uses  of  cassiterite  are  as  a  source  of  tin  for  plating  and 

the  manufacture  of  alloys. 

SUMMARY 

Cassiterite.  —  Sn02  ;  Sn  =  78  .  6  per  cent,  0=21.4  per  cent.  Tetragonal  ; 
holosymmetric.  a:c=  1:0.672.  (in),  (100),  (no),  (101),  (210),  (321); 
twinned  on  (101);  cleavage  parallel  (100)  imperfect;  brittle;  fracture 
sub-conchoidal. 

Hardness  =  6  .  5  ;  gravity  =7.  Brown  or  black;  streak  gray;  adaman- 
tine; translucent;  00=1.997;  double  refraction  positive;  c—  (0  =  0.097. 

Insoluble;  with  soda  on  charcoal  yields  tin. 

Cornwall,  Malay  Peninsula,  Wyoming,  and  Dakota. 

Rutile 

Rutile  (TiO2)  is  a  source  of  titanium,  an  element  used  for  giving 
a  yellow  color  to  glass,  for  hardening  steel,  and  for  various  chemical 
purposes.  Its  hardness  is  the  same  as  that  of 
cassiterite  (6.5),  and  its  color  and  form  are  very 
similar,  but  it  is  redder  (rutilus,  Latin  for  "red") 
and  has  a  yellowish-brown  streak  instead  of  a 
grayish  streak.  It  is  only  4  .  3  in  specific  gravity 
and  cleaves  readily  to  (100)  and  (no),  hence  is 
easily  distinguished  from  cassiterite.  It  occurs 
in  stout  crystals  (Nos.  3354  and  3355),  in  acicular 
and  twin  crystals,  and  in  masses  (No.  3197). 
The  stout  crystals  (Fig.  132),  nearly  duplicating 


those  of  cassiterite,  consist  of  the  following  planes:  (100),  (no),  (on), 
all  of  which  may    be   vertically    striated,    and    (in)    and   (101). 


no 


GUIDE  TO  MINERAL  COLLECTIONS 


Twinning  parallel  to  (on)  is  very  common  (Fig.  133)  and  the  twins 
are  often  repeated  six  or  eight  times  till  they  form  a  complete  ring 
with  the  different  individuals  inclined  to  each  other  in  a  zigzag  with 
angles  of  65°  35"  (Fig.  134). 

Acicular  crystals  varying  from  the  finest  threads  to  needles  and 
blades  of  some  thickness  often  penetrate  other  minerals  such  as  quartz. 


FIG.    133. — Rutile    triplet    twinned 
on  (on). 


FIG.    134. — Rutile    octet    twinned 
on  (on). 


The  beautiful  yellowish-red  or  brown  fibers  in  quartz  are  called 
fleches  d 'amour.  In  some  groups  the  needles  cross  each  other  at  the 
twinning  angle  and  form  a  reticulated  skeletal  plate  called  "sagenite" 
(=net). 

SUMMARY 

Rutile. — Ti02;  Ti=6o  per  cent,  0=40  per  cent.  Tetragonal;  holo- 
symmetric.  0:^=1:0.644.  (100),  (110),  (310),  (in),  (101);  twinned  on 
(101);  cleavage,  parallel  (100),  (no);  brittle;  fracture  uneven. 

Hardness  =  6. 5;  gravity  =  4. 3.  Reddish  brown;  streak  yellowish 
brown;  metallic;  adamantine;  translucent;  w=  2.616;  double  refraction 
positive  strong,  e  —  0^  =  0.287. 

Infusible;  insoluble. 

Switzerland,  Virginia,  North  Carolina,  Florida,  Arkansas,  Alaska. 


Pyrolusite 

Pyrolusite  (MnO2)  is  an  amorphous,  black,  soft  (hardness,  2) 
mineral  used  in  glass  manufacture  to  clear  the  glass  from  green  and 
brown  colors  (Nos.  541  and  1838).  Because  of  its  usefulness  in  this 


OXIDES  in 

respect  it  has  received  its  name  (irvp,  "  fire  " ;  Xueiu,  "  to  wash").    Large 
quantities  are  employed  also  as  a  flux  in  iron  manufacture. 

It  has  no  crystal  form  of  its  own,  but  borrows  its  form  of  manganite, 
from  which  it  is  derived  by  the  loss  of  water.  Brazil  and  Russia 
before  the  war  supplied  the  United  States  with  the  greatest  part  of 
the  manganese  ore  needed.  About  one  million  tons  of  ore  came 
from  Russia  in  1913.  In  1916  more  than  that  amount  was  produced 
in  the  United  States. 

SUMMARY 

Pyrolusite. — MnO2;  Mn  =  63.2  per  cent,  0  =  36.8  per  cent.  Pseu- 
domorph  after  manganite,  showing  radiated  fibrous  structure,  but  usually 
massive,  earthy,  soiling  the  fingers. 

Hardness=2;  gravity=5-     Gray  to  black;  streak  black. 

Infusible;  soluble  in  warm  hydrochloric  acid. 

Minnesota,  Arkansas,  California,  Virginia,  Russia,  Brazil. 


CLASS  VI.    CARBONATES 

CALCITE  GROUP 
CALCITE  GROUP  HEXAGONAL 

Calcite  CaCO3 

Dolomite  CaMg(CO3)2 

Magnesite  MgCO3 

Siderite  FeCO3 

Rhodochrosite  MnCO3 

Smithsonite  ZnCO3 
Calcite 

Calcite  is  one  of  the  most  important  and  interesting  minerals  in 
the  world,  both  because  of  its  beauty  and  abundance,  and  because  of 
its  usefulness  from  a  scientific  and  practical  standpoint.  The  history 
of  calcite  is  the  history  of  mineralogy.  In  abundance  it  is  surpassed 
by  quartz  alone.  Its  crystals  occur  in  such  profusion,  variety,  and 
beauty  as  easily  to  have  attracted  the  attention  of  mineralogists  and 
to  have  continually  furnished  them  with  material  for  study.  This 
study  has  led  to  important  results.  About  the  time  that  the  Dane, 
Steno,  noted  the  regularity  of  the  angles  on  quartz  and  announced 
the  law  of  the  constancy  of  angle,  a  countryman  of  his,  Erasmus 
Bartholinus  (1670),  was  working  with  the  splendid  calcite  crystals 
then  recently  discovered  in  Iceland  (No.  3832);  and  in  his  book 
Experimenta  Crystalli  Islandici  described  the  remarkable  cleavage 
and  the  double  refraction  which  calcite  shows  more  satisfactorily 
than  does  any  other  mineral. 

Twenty  years  later  the  Hollander  Huygens,  famous  for  his 
undulatory  theory  of  light,  extending  Bartholinus'  study  of  calcite, 
was  able  to  formulate  the  laws  of  double  refraction — the  laws  of  a 
phenomenon  which  could  not  be  explained  by  the  corpuscular  theory 
of  Newton.  For  many  years  following,  while  discussion  of  the  cor- 
puscular and  wave  theories  of  light  was  at  its  height,  calcite  was 
carefully  studied  by  the  advocates  of  both  theories.  As  the  result 
of  such  study  Malus  (1808)  discovered  the  polarization  of  light. 
Today  calcite  is  much  used  in  optical  researches  because  of  its  effect 
on  light,  being  employed  for  "nicol  prisms"  in  microscopes,  both  for 
purely  scientific  and  for  commercial  purposes. 

112 


PLATE  XXI 


a,  Calcite,  "dog-tooth  spar,"  Joplin,  Missouri 


b,  Calcite,  "Iceland  spar,"  showing  double  refraction 


CARBONATES 


No  mineral  shows  more  planes  and  combinations  of  planes  than 
does  calcite.  More  than  two  hundred  forms  and  seven  hundred  com- 
binations have  been  described.  There  are  four  distinct  habits  of 
crystallization — rhombohedral,  scalenohedral,  prismatic,  and  tabular. 
The  fundamental  form  is  the  rhombohedron,  R  (ion),  (Fig.  135),  in 
which  the  mineral  always  cleaves,  and  so  readily  that  it  is  difficult  to 
produce  a  fracture  in  any  other  direction  (Nos.  3460  and  3832).  As  an 
independent  form  this  plane  is  rare  but  is  found  on  crystals  from  near 
Bologna,  Italy,  and  is  a  predominant  form  on  the  calcite  from  Iceland 
("  Iceland  spar").  The  obtuse  rhombohedron, — ^R  (0112)  (Fig.  139), 
is  common.  Figure  137  represents  another  common  acute  rhombo- 
hedron. The  scalenohedron  which  furnishes  the  so-called  "dog 


FIG.  135. — Calcite.  Positive  rhombo- 
hedron (ioii)=R;  the  cleavage  rhom- 
bohedron. 


FIG.  136. — Calcite.     Negative  rhom- 
bohedron (oin)  =  —  R. 


tooth  spar"  (Fig.  138)  (Nos.  3446,  3458,  etc.)  is  a  form  of  frequent 
occurrence.  Prism  planes  also  appear  (No.  3450),  modified  usually 
with  rhombohedron  planes  as  in  Figure  139,  where  the  rhombohedron 
is  negative,  —  %R.  If  the  prisms  are  short  and  a  basal  plane  is 
present,  tabular  crystals  similar  to  Figure  140  result.  Sometimes 
they  are  as  thin  as  paper  and  grouped  parallel  to  one  another  so  as 
to  give  the  effect  of  cleavage  which  is  peculiar  to  slate,  hence  the 
variety  is  called  "  slate  spar."  Scalenohedrons  are  usually  modified 
by  rhombohedrons  (Fig.  141). 

All  these  forms  agree  in  having  three  planes  of  symmetry,  which 
are  diagonal  to  the  lateral  crystallographic  axes,  and  intersect  in  the 
vertical  axis  c,  the  axis  of  trigonal  symmetry.  Such  symmetry  is  so 
typical  as  to  have  been  named  after  calcite  the  "calcite  class." 


GUIDE  TO  MINERAL  COLLECTIONS 


There  are  four  types  of  twins:  (i)  A  common  type  is  that  in 
which  two  crystals  are  united  by  juxtaposition  on  the  basal  plane. 
Figure  142  shows  a  rhombohedron  and  Figure  143  a  scalenohedron 
twinned  according  to  this  law.  If  the  crystals  overlap,  filling  the 


FIG.  137. — Calcite.  Neg- 
ative acute  rhombohedron 
(0221)  =  — 2  R. 


FIG.  138.— Calcite, 
scalenohedron. 


FIG.  139. — Calcite, 
prism  and  negative 
obtuse  rhombohedron. 


FIG.  140. —  Calcite, 
showing  prism,  nega- 
tive obtuse  rhombo- 
hedron, and  base. 


FIG.    141. —  Calcite;         FIG.    142. —  Calcite. 

combination  of  scaleno-  Rhombohedron  twinned  on 

hedron  and  rhombohe-  (oooi). 
dron. 


re-entering  angles,  cleavage  lines  will  disclose  the  twinning.  (2)  More 
common  than  the  foregoing  is  that  type  whose  twinning  plane  is  —\R 
(0112).  In  this  case  the  cleavage  planes  of  the  two  individuals  are 
parallel.  Figure  144  shows  a  juxtaposed  twin  of  this  sort  charac- 
teristic of  crystals  from  Guanajuato,  Mexico.  Twinning  lamellae 


PLATE  XXII 


Calcite,  Joplin,  Missouri;  (2131)  and  (3145) 


PLATE  XXIII 


Calcite  scalenohedron,  Rossie,  St.  Lawrence  County,  New  York 


CARBONATES  115 

parallel  to  —%R  have  been  commonly  produced  in  calcite  by  pressure, 
and  in  thin  sections  under  the  microscope  are  so  characteristic  as  to 
furnish  the  best  means  of  distinguishing  the  mineral.  They  well 
illustrate  secondary  twinning  such  as  may  be  artificially  produced  in 
calcite  and  is  especially  pronounced  in  "  Iceland  spar."  (3)  The  type 
of  twinning  parallel  to  the  cleavage  rhombohedron  R,  though  rare,  is 
shown  in  scalenohedrons  and  prisms  (Figs.  145  and  146).  In  these 
twins  one  cleavage  plane  only  is  parallel  to  the  two  individuals. 


FIG.  143.— Cal- 
cite scalenohedron 
twinned  parallel 
to  (oooi). 


FIG.  144. — Calcite  scalenohedron 
twinned  parallel  to  (0112)  =  —%R. 


FIG.  145.— Calcite 
prism  twinned  par- 
allel to  R. 


(4)  The  type  where  the  twinning  plane  is  the  acute  negative  rhombo- 
hedron (0221)  produces  forms  which  closely  resemble  those  of  the 
second  class,  but  here  the  cleavage  planes  of  the  different  individuals 
are  not  parallel  (Fig.  147). 

Some  calcite  crystals  exhibit  asterism,  i.e.,  when  a  candle  flame  is 
viewed  through  them  it  appears  as  a  radiating  star  of  light.  This  is 
due  to  systems  of  hollow  tubes  parallel  to  each  other  in  three  direc- 
tions, and  is  produced  where  the  " gliding  surfaces"  of  the  negative 
rhombohedron  —%R  intersect  each  other. 

Calcite  is  useful  for  nicol  prisms  because  the  ordinary  ray  while 
passing  through  it  is  so  greatly  refracted  (00  =  1.658).  The  extraor- 
dinary ray  is  allowed  to  pass  through  the  prism,  being  but  slightly 
affected  by  the  Canada  balsam  whose  index  is  nearly  that  of  the 
extraordinary  ray.  (For  balsam  e  =  i .  536.) 


n6 


GUIDE  TO  MINERAL  COLLECTIONS 


A  microscopic  section  of  calcite  rotated  above  the  polarizer  when 
the  analyzer  is  removed  shows  high  relief  if  the  ordinary  ray  is  allowed 
to  pass  through,  and  relief  so  low  as  to  be  almost  invisible  when  the 
extraordinary  ray  passes  through. 

When  calcium  carbonate  crystallizes  from  aqueous  solution  in 
veins  or  other  cavities,  it  forms  the  ordinary  variety  of  calcite.  If  it 
is  deposited  from  springs  or  streams  by  evaporation  in  a  more  or  less 
granular  condition  it  forms  travertine,  calc  tufa,  stalactites,  and 
stalagmites.  If  it  is  composed  of  fragments  or  organic  remains 
cemented  by  calcareous  or  other  cements,  it  forms  chalk,  oolite,  and 


FIG.      146. — Calcite 
twinned  parallel  to  R. 


scalenohedron 


FIG.      147. — Calcite      scalenohedron 
twinned  parallel  to  (0221). 


limestone.  If  the  limestone  has  been  metamorphosed  by  heat  and 
pressure  so  as  to  become  crystallized,  it  forms  marble.  Among  some 
of  the  localities  the  following  are  famous  because  of  the  abundance 
and  beauty  of  their  crystallized  varieties.  In  Iceland  near  Eskif- 
jordhr  a  cavity  36  feet  long,  15  feet  wide,  and  10  feet  high  in  dolomite 
rock  was  found  filled  with  clear  crystallized  calcite.  The  prevailing 
forms  were  rhombohedrons  (ion)  with  edges  beveled  by  scaleno- 
hedrons  (2131)  and  (3145),  and  scalenohedrons  terminated  by  (1011) 
or  (3145).  Their  surfaces  were  often  corroded  or  coated  with  other 
minerals  such  as  stilbite. 

In  England  the  lead,  iron,  and  ftuorite  mines  of  Derbyshire,  Dun- 
ham, and  Cumberland  (Nos.  3450,  3451,  and  3452)  have  furnished 
fine  crystals  which  now  ornament  museums  in  all  parts  of  the  world. 
Many  beautiful  crystals  come  from  the  Hartz  Mountains.  They  are 


PLATE  XXIV 


a,  Calcite,  Joplin,  Missouri;    (2131)  and  (3145) 


b,  Quartz  geode  with  large  flat  rhombohedral  crystals,  St.  Francisville,  Missouri 


CARBONATES  117 

commonly  prismatic  planes  and  tabular  forms.  The  silver  mines  of 
Guanajuato,  Mexico,  have  furnished  twin  crystals  of  great  beauty 
and  variety.  Among  many  famous  localities  in  the  United  States 
may  be  mentioned  St.  Lawrence  County,  New  York  (No.  4657);  the 
Lake  Superior  copper  mines  with  their  complex  crystals  which  often 
contain  spangles  and  wires  of  copper;  and  the  Wisconsin,  Illinois 
(Nos.  698  and  699),  and  Missouri  (No.  3459,  etc.)  lead  and  zinc 
mines  with  their  rhombohedrons  and  scalenohedrons.  The  geodes  of 
Keokuk  contain  numerous  large  flat  crystals  (Nos.  686,  691,  672). 
At  Joplin,  Missouri,  many  large,  beautiful,  honey-yellow  scaleno- 
hedrons (2131)  terminated  by  rhombohedrons  R  (1011)  and  the 
striated  —  %R  have  been  found.  The  acute  terminal  edges  of  these 
scalenohedrons  (2131)  are  often  replaced  by  striated  and  rounded 
faces  (Nos.  3886,  3899,  3890,  also  Plate  XXIII). 

SUMMARY 

Calcite. — CaCO3;  CaO  =  s6  per  cent,  CO2=44  per  cent.  Hexagonal; 
symmetry  dihexagonal  alternating  (calcite  class);  a :c=  1:0.854.  R, 
—%R,  4R;  twinned  on  (oooi),  (0112),  (1011),  (0221).  Cleavage  parallel 
R  perfect;  brittle;  fracture  conchoidal. 

Hardness  =  3;  gravity  =2. 7  2.  Colorless;  vitreous;  transparent; 
refraction  strong,  (0  =  1.658;  double  refraction  very  strong,  positive, 
<o— 6=0.172. 

Infusible;  soluble  with  effervescence  in  cold  hydrochloric  acid,  diluted 
to  one-third  strength. 

Ubiquitous. 

Dolomite 

Dolomite  can  be  distinguished  from  calcite,  which  it  very  closely 
resembles,  from  the  fact  that  it  is  harder  (hardness,  3.5),  heavier 
(gravity,  2.85),  and  does  not  effervesce  in  cold  hydrochloric  acid 
diluted  to  one-third  strength,  except  when  finely  powdered.  Though 
strongly  resembling  each  other  in  crystal  form,  calcite  and  dolomite 
differ  in  this  respect,  that  while  calcite  has  dihexagonal  alternating  sym- 
metry, dolomite  has  hexagonal  alternating  symmetry  (dioptase  class), 
i.e.,  it  lacks  all  planes  of  symmetry,  and  the  vertical  axis  is  an  axis  of 
trigonal  symmetry.  This  becomes  evident  when  the  two  minerals  are 
etched  with  acid  and  when  their  axes  of  elasticity  are  measured.  If 
rhombohedrons  of  calcite  and  dolomite  are  placed  in  dilute  hydrochloric 


n8 


GUIDE  TO  MINERAL  COLLECTIONS 


acid,  upon  the  surface  appear  depressions  which  show  the  symmetry 
of  the  crystals.  The  depressions  on  calcite  (Fig.  148)  indicate 
three  planes  of  symmetry,  since  each  etched  figure  has  one  line  of 
symmetry  parallel  to  the  shorter  diagonal  of  the  rhombohedron, 
showing  that  a  plane  of  symmetry  is  perpendicular  to  that  face.  A 
dolomite  rhombohedron  treated  in  the  same  manner  is  marked  with 
pits  unsymmetrical  in  outline  (Fig.  149),  indicating  that  there  is  no 
plane  of  symmetry  perpendicular  to  the  rhombohedron.  The  figures 
on  the  three  upper  faces  are  related  to  each  other  as  are  a  right- 
handed  and  a  left-handed  glove,  the  lower  ones  appearing  as  if  they 
were  reflections  of  the  upper  (enantiomorphous).  This  indicates 
that  the  crystal  has  one  hexagonal  axis  of  alternating  symmetry,  a 


FIG.  148. — Calcite  etched  with  dilute 
hydrochloric  acid. 


FIG.     149. — Dolomite     etched    with 
dilute  hydrochloric  acid. 


fact  which  is  also  shown  by  rhombohedron  planes  which  are  some- 
times developed  upon  the  alternate  edges  of  the  usual  rhombohedron. 
The  difference  in  the  symmetry  of  calcite  and  dolomite  is  also 
indicated  by  their  coefficients  of  elasticity.  These  coefficients  are  ob- 
tained by  cutting  bars  of  the  minerals,  supporting  them  on  knife  edges, 
applying  a  weight  sustained  by  a  knife  edge,  and  measuring  the 
amount  of  bending  by  microscopic  or  other  means.  When  lines  are 
drawn  on  a  rhombohedral  face  proportional  to  the  amount  of  bend- 
ing and  the  ends  connected,  curves  shown  in  Figures  150  and  151  are 
produced.  In  calcite  the  elasticity  is  symmetrically  arranged  parallel 
to  the  diagonal  of  the  rhombohedron.  In  dolomite  it  is  unsym- 
metrical. Thus  etching  and  measuring  of  elasticity  show  that  the 
rhombohedrons  are  not  perpendicular  to  planes  of  symmetry  in 
dolomite.  Further,  in  calcite  it  was  seen  that  —^(0112)  is  a  glide 
plane,  or  plane  of  secondary  twinning,  as  shown  by  the  series  of 


CARBONATES 


119 


hollow  tubes  arranged  parallel  to  this  plane  and  appearing  as  fine 
lamellae  under  the  microscope.  The  presence  of  this  glide  plane  can 
be  discovered  by  pressing  a  knife  into  a  cleavage  rhombohedron 
across  one  of  the  terminal  edges.  By  the  pressure  the  molecules  are 
revolved  180°  into  a  new  twinning  plane,  so  that  the  other  lamellae 
are  parallel  to  —  %R  (Fig.  152).  In  dolomite  —%R  is  not  a  plane  of 
secondary  twinning. 

Dolomite  is  a  double  salt  of  calcium  and  magnesium — a  molecule 
of  each  carbonate  being  united  to  form  it.  If  it  were  an  isomorphous 
mixture  of  the  two  carbonates  in  molecular  proportions,  its  crystalliza- 
tion would  be  the  same  as  that  of  calcite  and  magnesite.  However, 
it  is  different,  and  it  would  have  a  specific  gravity  of  2  .843.  But  it 


FIG.    150. — Elasticity   coefficient    of          FIG.    151. — Elasticity    coefficient    of 
calcite.  dolomite. 

is  heavier  (gravity,  2.85),  just  as  would 
be  expected,  since  while  the  double  salt  is 
forming  there  is  a  contraction  of  the  two 
carbonates  which  increases  their  specific 
gravity. 

Dolomite   occurs   in   well-crystallized 
forms    deposited    from   solution   and    in 
masses  made  of  fragments  of  organic  re- 
mains  which  have   been   more  or   less   altered   and  cemented    by 
chemicals  in  solution.      The  massive  variety  forms  extensive  beds 
which  extend  for  miles  over  the  country. 

Vermont,  New  Jersey,  and  New  York  (No.  3217,  etc.)  furnish 
many  crystals.  Saddle-shaped  crystals  are  abundant  in  Joplin, 
Missouri  (No.  3464).  The  greater  part  of  the  limestone  of  Illinois 
is  dolomitic. 


FIG.   152. — Glide  planes 
in  calcite. 


120  GUIDE  TO  MINERAL  COLLECTIONS 

SUMMARY 

Dolomite. — CaMg(CO3)2;  CaO  =  3o.4  per  cent,  MgO  =  2i.y  per  cent, 
CO2  =  47-9  per  cent.  Hexagonal;  symmetry  hexagonal  alternating; 
0:^=1:0.832.  (1011);  cleavage  parallel  (1011)  perfect;  brittle;  fracture 
conchoidal. 

Hardness  =  3. 5;  gravity  =2. 85.  Colorless,  streak  white;  vitreous; 
transparent.  Refraction  strong,  00=1,682;  double  refraction  strong, 
negative,  co— €  =  0.189. 

Infusible;  soluble  with  effervescence  in  warm  acids. 

Tyrol,  Switzerland,  England,  Vermont,  New  Jersey,  New  York, 
Missouri. 

Magnesite 

The  pure  magnesium  carbonate  is  a  white  brittle  mineral,  usually 
massive,  granular,  and  earthy.  It  is  harder  than  either  of  the  two 
other  members  of  the  group  thus  far  described  (hardness,  4)  and 
heavier  (gravity,  3.1).  Before  the  world- war  this  mineral,  obtained 
mainly  from  Greece  (No.  3466),  furnished  a  large  part  of  the  mag- 
nesium needed  in  the  arts  and  manufactures.  Recently  magnesite 
from  Quebec,'  California,  etc.,  has  been  used;  also  dolomite  and  the 
waters  from  which  sodium  chloride  had  been  extracted. 

SUMMARY 

Magnesite. — MgCO3;  MgO  =  4y.6  per  cent,  CO2=52.4  per  cent. 
Hexagonal;  a:c=  1:0.8112.  Massive,  granular,  earthy;  brittle;  fracture 
sub-conchoidal.  White;  vitreous;  silky;  transparent  to  opaque. 

Infusible;  effervesces  in  warm  hydrochloric  acid.  Common  decom- 
position product  of  ferromagnesian  silicates. 

Greece,  Canada,  California,  Washington,  Maryland. 

Siderite 

Siderite,  FeCO3,  which  furnishes  almost  no  iron  in  the  United 
States,  is  an  important  iron  ore  in  Germany  (No.  4512),  and  the 
most  important  source  of  iron  in  England.  When  pure  it  occurs  in 
brown,  vitreous,  translucent  rhombohedrons,  or  in  fibrous  botryoidal 
or  globular  forms.  The  rhombohedrons  are  often  curved  and  some- 
times acute.  Large  basal  planes  give  rise  to  a  tabular  variety  which 
often  has  zonal  structure  caused  by  hexagonal  bands.  Being  liable 
to  oxidation,  the  mineral  readily  loses  its  gray  color,  becomes  brown, 


CARBONATES  1 21 

and  changes  into  limonite.     The  dehydration  of  limonite  produces 
hematite  and  finally  magnetite. 

Among  European  localities,  Cornwall  and  Freiburg  are  the  most 
productive  of  siderite,  while  in  the  United  States  the  Appalachian 
regions  have  furnished  the  largest  supplies.  Of  recent  years  Ohio- 
has  been  the  leading  producer. 

SUMMARY 

Siderite.— FeC03;  FeO  =  62.i  per  cent,  CO2=37.o.  per  cent.  Hex- 
agonal; symmetry,  dihexagonal  alternating;  a:c=  i  :o.  818.  (1011),  (oooi); 
faces  curved;  fibrous,  globular.  Cleavage  parallel  (1011)  perfect;  brittle; 
fracture  sub-conchoidal. 

Hardness=3.5;  gravity =3. 8.  Brown;  vitreous,  translucent.  Re- 
fraction very  strong,  00=1.878;  double  refraction  very  strong,  negative 
<o— €=0.241. 

Fuses  at  4.5  to  black  magnetic  globule.  Effervesces  in  warm  hydro- 
chloric acid. 

Cornwall,  Freiburg,  Ohio,  Appalachians. 

Rhodochrosite 

Beautiful  rose-pink  rhombohedrons  of  rhodochrosite  are  found  in, 
Colorado  (Nos.  3471  and  3472),  the  Ural  Mountains,  and  other 
places  where  solutions  carrying  manganese  carbonates  have  for  some 
cause  slowly  given  up  their  burden.  The  reddish  color  of  rhodo- 
chrosite easily  distinguishes  it  from  the  other  carbonates. 

SUMMARY 

Rhodochrosite. — MnCO3;  MnO  =  6i.7  per  cent,  0)2=38.3  per  cent. 
Rounded  (1011),  massive,  compact.  Cleavage  parallel  (1011)  perfect; 
brittle;  fracture  uneven. 

Hardness=4;  gravity =3. 5.    Rose  red;  translucent;  negative. 

Infusible.     Effervesces  in  warm  hydochloric  acid. 

Russia,  Hungary,  Saxony,  Belgium,  New  Jersey,  Colorado. 

Smithsonite 

The  physical  condition,  that  is,  the  form,  cleavage,  fracture, 
hardness,  weight,  luster,  diaphaneity,  and  optical  properties  of  the 
zinc  carbonate,  smithsonite,  closely  resemble  that  of  the  other  mem- 
bers of  the  group.  Smithsonite  is  sometimes  colorless,  but  more 


122  GUIDE  TO  MINERAL  COLLECTIONS 

usually  green  (No.  3751),  blue,  or  brown  from  the  presence  of  copper, 
iron,  or  other  foreign  substances.  It  is  used  as  a  zinc  ore  in  the 
Mississippi  Valley  region,  as  well  as  in  other  places.  In  northern 
parts  of  Illinois  it  formerly  produced  upward  of  a  thousand  dollars' 
worth  of  zinc  annually. 

SUMMARY 

Smithsonite. — ZnCO3;  ZnO=64.8  per  cent,  CO2=35.2  per  cent. 
Usually  botryoidal,  reniform,  granular,  earthy. 

Hardness=5;  gravity  =  4. 4.     White,  green,  blue,  brown,  vitreous. 

Infusible;  gives  zinc  coating  with  soda  on  charcoal.  Effervesces  in 
warm  hydrochloric  acid. 

Many  European  localities,  Wisconsin,  Illinois,  Iowa,  Missouri, 
Arkansas.  

The  calcite  group  furnishes  one  of  the  best  illustrations  of  iso- 
morphism which  the  mineral  kingdom  affords,  since  the  carbonates  of 
calcium,  magnesium,  iron,  manganese,  and  zinc,  all  different  chemical 
substances,  assume  practically  the  same  form.  All  the  members  of 
the  group  are  rhombohedral  in  form,  practically  identical  in  cleavage, 
very  similar  in  hardness  and  gravity.  All  effervesce  in  warm  hydro- 
chloric acid.  The  following  group,  the  aragonite  group,  all  of  whose 
members  are  orthorhombic,  is  another  illustration  of  isomorphism. 

ARAGONITE  GROUP 

ARAGONITE  GROUP  ORTHORHOMBIC 
Aragonite  CaCO3 

Witherite  BaCO3 

Strontianite  SrCO3 

Cerussite  PbCO3 

Aragonite 

The  orthorhombic  form  of  calcium  carbonate,  named  from 
Aragon  in  Spain  where  it  was  first  found,  is  much  less  common  than 
calcite.  Its  comparative  rarity  may  be  due  to  two  causes:  (i)  to 
the  conditions  necessary  for  its  formation;  and  (2)  to  its  instability. 
One  of  the  conditions  necessary  for  its  formation  is  that  the  solution 
from  which  it  is  deposited  must  be  hot,  whereas  calcite  is  usually 
deposited  from  cold  waters.  This  is  shown  when  the  two  minerals  are 
made  in  the  laboratory  and  by  the  conditions  which  surround  aragonite 


PLATE  XXV 


a,  Aragonite  crystals  four  inches  in  diameter,  Cianciana,  Sicily 


b,  Stalactites,  Bisbee,  Arizona 


CARBONATES 


123 


in  the  field  and  by  its  associations.  Aragonite  very  often  accom- 
panies sulphur  crystals,  which  are  commonly  deposited  in  volcanic 
regions  from  hot  solutions.  There  are  exceptions,  such  as  the  calcium 
carbonate  deposited  by  living  organisms  in  the  shells  of  mollusks, 
which  is  in  the  form  of  aragonite.  Further,  if  a  calcium  carbonate 
solution  contains  a  minute  quantity  of  a  soluble  sulphate  or  ortho- 
rhombic  carbonate,  aragonite  crystals  may  be  formed.  Aragonite  is 
less  stable  than  calcite,  readily  changing  its  crystal  form  at  ordinary 
temperature. 

When  one  mineral  changes  into  another  of  the  same  composition 
by  simply  altering  its  form,  it  is  called  a  paramorph.  When  it 
changes  into  the  form  of  a  mineral  of  different  composition  it  is  called 
a  pseudomorph.  For  example,  a  quartz  crystal  which  assumes  the 
cubic  shape  of  fmorite  is  said  to  be  a  pseudomorph  after  fluorite.  An 
aragonite  crystal  which  takes  the  form  of  calcite  is  said  to  be  a 
paramorph.  A  paramorph  can  be  detected,  for  example,  when  an 
aragonite  crystal  is  but  partially  paramorphosed,  the  inner  portion 
being  aragonite  and  the  outer  calcite.  Paramorphism  is  possible 
only  among  minerals  which  exhibit  dimorphism  or  polymorphism. 
Aragonite  and  calcite  were  the  earliest  recognized 
examples  of  dimorphism  in  the  mineral  kingdom. 

Aragonite  rarely  occurs  in  simple  ortho- 
rhombic  crystals.  It  is  nearly  always  twinned 
parallel  to  the  prism  in  such  a  manner  as  to 
produce  seemingly  hexagonal  forms.  Nearly  all 
calcium  carbonate  which  is  fibrous,  stalactitic, 
botryoidal,  or  concretionary  is  classified  as  aragon- 
ite. For  example,  the  stalactites  of  Mammoth 
Cave  and  other  caves  (Nos.  2118,  2119),  the 
pisolites  of  Carlsbad  and  other  hot  springs,  and 
the  beautiful  white  coral-like  groups  from  Wind  Cave,  South  Dakota 
(No.  3176),  and  Bisbee,  Arizona,  are  aragonite. 

Aragonite  can  be  distinguished  from  calcite  when  the  crystal  form 
is  not  evident  by  its  superior  hardness  and  weight. 

Simple  crystals  (Fig.  153)  are  composed  of  prisms,  brachypina- 
coids,  and  dome  planes.  Groups  of  crystals  with  predominance  of 
acute  pyramids  (441),  (991),  and  (081),  (091),  showing  horizontal 
striations,  are  common.  If  three  crystals  such  as  shown  in  Figure  154 


0*° 


FIG.  153. — Aragonite 


124 


GUIDE  TO  MINERAL  COLLECTIONS 


interpenetrate  parallel  to  the  prism  plane  and  the  re-entering  angles 
are  filled  in,  a  form  having  the  cross-section  shown  in  Figure  155 
and  resembling  a  hexagonal  prism  is  produced.  Large,  white, 
yellowish  prisms  of  this  sort  are  found  at  Girgenti  and  Cianciana, 
Sicily  (No.  3902),  and  at  the  sulphur  mines  in  Hungary.  At  Aragon, 
Spain,  the  crystals  are  corroded  and  are  found  in  red  ferruginous  marl 
with  gypsum  and  quartz.  Nos.  2116  and  2120  show  stalactites  from 
Chester,  Illinois;  No.  2117,  aragonite  as  fossilizing  material  at  the 
same  locality;  Nos.  2672,  2685,  examples  from  Rock  Island;  No.  3469 


FIG.  154.  —  Basal  section  of  aragonite 
triplet. 


FIG.  155.  —  Basel  section  of  aragonite; 
interpenetrant  triplet. 


shows  botryoidal  masses  from  Quincy;  No.  3176  from  the  Black 
Hills;  Nos.  3467  and  3468  are  from  Fort  Collins.  Carlsbad,  Bohemia, 
is  also  represented.  No.  3902  is  an  unusually  fine  group  consisting 
of  two  large  crystals  of  interpenetrating  triplets  and  several  smaller 
imperfect  crystals.  The  largest  crystal  measures  about  four  inches 
in  diameter  and  is  two  inches  high. 

SUMMARY 

Aragonite. — CaCO3;  CaO  =  $6  per  cent,  CO2  =  44  per  cent.  Ortho- 
rhombic.  a:6:c  =  o.628:io.72i.  (no),  (oio),  (on),  (ooi),  (in);  twinned 
on  (no);  cleavage  (oio),  (no)  imperfect;  brittle;  fracture  sub-conchoidal. 

Hardness  =  3.5;  gravity  =2.9.  Colorless ;  vitreous ;  transparent ; 
mean  angle  of  refraction,  (3=  1.682,  the  least,  a=  1.530.  Double  refrac- 
tion very  strong,  negative,  i.e.,  difference  between  the  greatest  angle  of 
refraction,  y,  and  the  least,  a,  is  o.  156. 

Infusible;  effervesces  in  hydrochloric  acid. 

Spain,  Sicily,  Cordilleran  states. 


CARBONATES 


125 


Witherite 

This  carbonate  of  barium  occurs  in  white,  heavy,  not  very 
abundant  crystals  and  masses.  The  crystals  appear  to  be  hexagonal 
pyramids  (Fig.  156),  but  a  thin  section  cut  parallel  to  the  base 
(Fig.  157)  shows  that  the  seemingly  simple"  crystal  is  composed  of 
three  orthorhombic  crystals,  twinned  parallel  to  prism  planes  and 
hence  crossing  each  other  at  angles  of  62° — the  angle  between  the 
prism  planes.  Upon  the  pyramid  planes  are  more  or  less  prominent 
striations  caused  by  the  growth  of  a  succession  of  different  capping 


FIG.  156.— Witherite 


FIG.  157. — Cross-section  of  witherite 


pyramids.  The  pyramid  planes  vary  in  their  intercepts  on  the  c  axis 
and  produce  both  acute  and  obtuse  forms.  In  addition  to  well- 
formed  crystals  there  are  aggregates  made  up  of  acicular  crystals, 
grouped  into  botryoidal  and  reniform  shapes.  Compact  masses  are 
the  most  characteristic  form  of  the  mineral. 

The  luster  of  the  fresh  crystals  is  greasy,  but  is  changed  when 
sulphur  fumes  or  solutions  coat  the  surface  with  barium  sulphate, 
changing  it  into  a  dull  white. 

Witherite  may  be  distinguished  from  minerals  of  similar  appear- 
ance by  the  fact  that  it  is  heavy,  effervesces  in  cold  hydrochloric 
acid,  and  colors  the  blowpipe  flame  green.  Great  quantities  are  pro- 
duced in  two  northern  counties  in  England,  where  it  was  discovered 
0-1783  by  the  mineralogist  after  whom  it  was  named,  Withering,  and 
where  it  has  been  mined  for  more  than  one  hundred  years.  Witherite 
is  used  for  medicinal  and  industrial  purposes.  Large  quantities  are 
employed  in  the  manufacture  of  rat  poison. 


126  GUIDE  TO  MINERAL  COLLECTIONS 

SUMMARY 

Wither ite, — BaCO3 ;  BaO  =  7  7 . 7  per  cent,  CO2  =22.3  per  cent.  Ortho- 
rhombic;  holosymmetric.  a:  &:c  =  o.  603: 1:0.730.  (no),  (oio),  (on). 
Common  form  pseudohexagonal  bipyramid  produced  by  interpenetration 
twinning  of  three  individuals  at  angles  of  62°;  twinning  plane  (no). 
Brittle;  fracture  uneven. 

Hardness  =  3. 5;  gravity  =  4. 3.  Colorless;  streak  white;  vitreous; 
translucent.  Double  refraction  negative,  weak;  axial  plane  parallel 
(oio);  acute  bisectrix  perpendicular  to  (ooi).  2  £=26°  30'. 

Fusible  (2) ;  effervesces  in  hydrochloric  acid. 

Northumberland  and  Cumberland,  England;  Kentucky,  Michigan. 

Strontianite 

Strontianite  very  closely  resembles  aragonite  in  color,  streak, 
luster,  and  form,  but  differs  in  being  heavier  (gravity,  3.7)  and  in 
yielding  the  intense  red  color  characteristic  of  strontium  when  heated 
in  the  blowpipe  flame. 

Strontianite  is  sometimes  colorless  and  transparent,  but  more 
often  translucent  and  white,  green,  yellow,  or  brown.  Its  fibrous, 
acicular,  or  columnar  crystals  are  rarely  well  defined  or  terminated. 
They  are  usually  vertically  striated.  The  same  kind  of  twinning 
occurs  as  is  so  common  for  aragonite  and  witherite,  viz.,  interpenetrant 
triplets  forming  pseudohexagonal  prisms  or  pyramids. 

At  Strontian  on  the  west  coast  of  Scotland  in  1791  a  mineral  was 
found  that  contained  a  new  element.  The  element  was  named 
strontium  and  the  mineral  Strontianite. 

Strontianite  finds  limited  use  as  a  source  of  red  lights  for  fire- 
works and  in  the  refining  of  beet  sugar. 

SUMMARY 

Strontianite. — SrCO3;  SrO=7o.i  per  cent,  CO2=2p.9  per  cent. 
Orthorhombic;  holosymmetric.  a : b: c=o.  6090:1:0.  7239.  (no),  (oio), 
(on);  fibrous,  acicular,  columnar,  granular;  cleavage  parallel  (no) 
nearly  perfect ;  brittle;  fracture  uneven. 

Hardness =3.5;  gravity =3.7.  Colorless,  white,  green,  yellow,  brown. 
Optically  negative;  axial  plane  parallel  to  (100);  bisectrix  perpendicular 
to  (ooi).  2  E=i2°  17'. 

Fusible;  soluble  in  hydrochloric  acid. 

Scotland,  Appalachian  states. 


CARBONATES 


127 


Cerussite 

Cerussite,  like  aragonite,  witherite,  and  strontianite,  simulates 
crystals  of  the  hexagonal  system,  while  in  reality  its  molecules 
arrange  themselves  in  accordance  with  the  laws  of  the  orthorhombic 
system.  Simple  crystals  of  cerussite  are  more  abundant  than  are 
those  of  witherite  and  strontianite.  The  most  common  habit  is  the 
form  produced  by  pyramids,  domes,  short  prisms,  and  pinacoids 
(Fig.  158),  and  the  tabular  crystals  like  those  in  Figure  159,  in  which 
the  domes  are  elongated  parallel  to  the  a  axis  and  the  pinacoid  is  the 
predominant  plane. 

The  commonly  occurring  interpenetrant  twinning  of  three  crystals 
parallel  to  prism  planes  produces  raylike  pyramids  (Fig.  160). 


FIG.  158. — Cerussite  FIG.  159. — Cerussite 


HO 


FIG.  1 60. — Three  cerus- 
site crystals  interpenetrat- 
ing parallel  to  prism  planes. 


Besides  pyramids  and  tabular  crystals,  single  and  combined,  acicular 
and  fibrous  masses  are  of  common  occurrence.  All  these  crystals 
when  fresh  have  smooth,  bright,  lustrous  surfaces.  Silky  or  adaman- 
tine luster  is  characteristic  of  lead  minerals.  The  best  specimens  have 
been  obtained  from  Bohemia,  Hungary,  New  South  Wales,  and 
Idaho,  where  they  are  found  on  galena  and  other  lead  ores,  from 
which  they  have  resulted  by  the  decomposition  of  galena. 

SUMMARY 

Cerussite.— PbC03;  PbO  =  83 . 5  per  cent,  CO2=  16 .  5  per  cent.  Ortho- 
rhombic;  holosymmetric;  0:6:^  =  0.610:1:0.723.  (no),  (oio),  (in), 
(021);  twinned  on  (no);  cleavage  parallel  (no),  (021)  imperfect;  brittle; 
fracture  conchoidal. 


p/- 


128  GUIDE  TO  MINERAL  COLLECTIONS 

Hardness  =  3.5;  gravity =6.5.  Colorless ;  streak  white ;  adamantine ; 
transparent;  18=2.076,  a  =1.804;  double  refraction  strong,  negative; 
y— a  =  0.2 74;  axial  plane  (oio);  acute  bisectrix  perpendicular  to  (ooi). 
2  £=17°  8.' 

Fusible;  soluble  in  nitric  acid. 

Cordilleran  states. 

Malachite 

Malachite  (juaXdx??,  "mallow  or  willow  tree")  is  a  basic  copper 
carbonate,  which  is  readily  recognized  because  of  its  vivid  green 
color.  Fine  compact  nodular  masses  composed  of  radial  fibers  have 
been  found  in  such  quantities  in  the  Ural  Mountains  (No.  3407)  and 

so  rarely  in  other  European  localities 
that  they  have  furnished  the  rulers 
of  Russia  a  unique  and  much-prized 
material  for  gifts.  In  palaces  and 
'\  museums  in  all  the  capitals  of 

\  Europe  the  tourist  sees  vases,  tables, 

and  other  ornaments  made  of  this 
striking  green  mineral.  They  are 
usually  recorded  as  "a  gift  from  the 
Czar  of  Russia."  In  many  European 
and  American  localities  malachite  (Nos. 
FIG.  161.— Axes  of  monoclinic  34Q5j  34o6)  QCCurs  in  such  quantities 

as  to  furnish  a  useful  source  of  copper. 

When  crystallized  under  favorable  conditions,  in  cavities,  for  example, 
it  forms  fine  fibrous  needles  which  build  tufts  as  soft  in  appearance  as 
velvet  (velvet  malachite).  Radiating  fibers  fill  winding  cavities  so 
as  to  look  like  roots  of  trees  when  exposed.  The  granular  and  earthy 
forms  of  malachite  are  the  most  abundant.  Well-formed  crystals  are 
almost  unknown,  but  acicular  prisms  disclose  the  fact  that  the  mole- 
cules have  so  arranged  themselves  as  to  produce  forms  characteristic 
of  the  monoclinic  system. 

In  this  system  the  molecular  structure  is  represented  by  three  axes 
of  unequal  length  (Fig.  161).  The  angle  j3  which  the  a  axis  makes 
with  the  c  axis  is  greater  then  90°.  The  a  and  7  angles  are  right 
angles.  Planes  constructed  upon  these  axes  produce  figures  having 
a  plane  of  symmetry  parallel  to  c  and  a,  and  an  axis  of  symmetry 


CARBONATES 


129 


which  is  the  c  axis.  The  forms  which  constitute  the  system  are 
analogous  to  those  of  the  orthorhombic  system.  They  are  pyramids 
(in),  prisms  (no),  orthopinacoids  (straight  pinacoids)  (100),  clino- 
pinacoids  (inclined  pinacoids)  (oio),  orthodomes  (101),  and  clino- 
domes  (on).  As  in  the  orthorhombic  system,  closed  forms  are 
obtained  by  combinations  of  two  or  more  kinds  of  planes  in  all  cases 
except  that  of  the  pyramid  (Fig.  162).  In  Figure  163  orthodomes 
are  united  with  clinodomes  to  produce  a  complete  form.  Figure  164 
shows  a  combination  of  prism  and  base. 

Malachite  does  not  well  illustrate  the  crystallography  of   the 
monoclinic  system.     To  understand  its  crystals  it  is  necessary  to 


.A.-.-J1'— \- £+1r 


FIG.  162. — Monoclinic  bipyramid 


FIG.  163. — Orthodomes  and  clinodomes 


resort  to  the  microscope.  Indeed,  with  any  transparent  mineral 
employment  of  optical  means  of  investigation  contributes  greatly  to 
the  knowledge  of  its  crystallography.  Sections  of  minerals  cut  at 
various  angles  are  cemented  with  Canada  balsam  to  pieces  of  glass 
and  ground  till  thin  enough  (about  one-hundredth  of  an  inch  in 
thickness)  to  permit  light  to  pass  through  them.  Examined  under 
the  microscope,  first  with  the  light  vibrating  in  all  directions,  then 
with  light  made  to  vibrate  in  but  one  direction  by  means  of  a  calcite 
prism  ("Nicol  prism"),  and  studied  with  light  passing  through  the 
mineral  with  parallel  rays  and  then  with  converging  rays,  the  crystal 
structure  becomes  clear.  Such  an  examination  of  malachite  reveals 
the  fact  that  there  are  two  directions  in  which  light  is  not  doubly 
refracted,  that  these  directions  are  in  the  plane  (axial  plane)  parallel 


130 


GUIDE  TO  MINERAL  COLLECTIONS 


to  the  clinopinacoid,  that  they  form  an  angle  of  nearly  90°  with  each 
other  (2  E  =  Sg°  18'),  that  the  line  which  divides  this  angle  (called 
the  acute  bisectrix)  forms  an  angle  of  32°  50'  with  the  c  axis,  and 


FIG.  164. — Model  of  prism  and  basal          FIG.  165. — Malachite  section  parallel 
plane.  to  (oio). 


that  the  angle  between  c  and  a,  the  /3  angle,  is  61°  50'.  A  cross- 
section  of  a  malachite  crystal  (Fig.  165)  parallel  to  the  clinopinacoid 
shows  the  relationship  of  these  various  directions. 

SUMMARY 

Malachite.— CuC03-Cu(OH)2;  €110  =  71.9  per  cent,  CO2=ig.9  per 
cent,  H2O  =  8.2  per  cent.  Monoclinic;  a:b:c=o. 881:1:0.401.  (3  = 
61°  50'.  (i.io),  (ooi);  twinned  parallel  (100);  cleavage  (oio),  (ooi)  per- 
fect; brittle;  fracture  uneven. 

Hardness  =  3 .  5 ;  gravity =4.  Green;  adamantine;  silky;  dull;  trans- 
lucent. (3  =  i .  88 ;  double  refraction  negative ;  y — a  =  o .  2 . 

Easily  fusible;  soluble  in  hydrochloric  acid. 

Urals,  Cordilleras. 


CARBONATES 


Azurite 

Azurite  is  another  basic  carbonate  of  copper  conspicuous  because 
of  the  beauty  of  its  color,  which  is  a  deep  azure  blue.  In  composition 
it  differs  from  malachite  in  having  less  copper  oxide.  Azurite  has 
69 . 2  per  cent,  malachite  71 .9  per  cent.  Azurite  by  increase  in  water 
content  changes  to  malachite,  increasing 
about  one- third  in  bulk,  thus  affording  an 
illustration  of  a  chemical  action  which 
would  tend  to  rend  inclosing  minerals  or 
rock.  Azurite  crystals  partially  changed 
into  malachite  are  of  common  occurrence. 
Both  of  these  minerals  result  from  decom- 
position of  copper  sulphides,  are  useful  ores 
of  copper,  and  are  found  in  the  same  local- 
ities. Azurite  occurs  in  good  monoclinic 
crystals  in  which  the  prism  (no)  and  base 
(on)  predominate,  modified  by  pyramids 
(in)  and  domes  (013)  (Fig.  166).  Chessy 

near  Lyons,  France,  and  Bisbee,  Arizona  (Nos.  3409,  3410),  are  noted 
for  their  fine  crystals. 

SUMMARY 

Azurite.— 2CuCO3-Cu(OH)2;  CuO  =  6g.2  per  cent,  CO2=25.6  per 
cent,  H2O  =  5.  2  per  cent.  Monoclinic;  a:&:c  =  o. 85:1:1.  76;  0  =  87°  36'. 
(no),  (ooi),  (in),  (103);  cleavage  parallel  (on)  fair;  brittle;  fracture 
conchoidal. 

Hardness=4;  gravity =3. 8.  Deep  to  light  blue;  vitreous;  trans- 
lucent in  thin  pieces.  Double  refraction  positive;  y— a  =  0.2..  Axial 
plane  perpendicular  to  (oio);  acute  bisectrix  makes  an  angle  of  75°  with  a 
and  lies  in  the  supplementary  angle  to  /?. 

Easily  fusible  (2) ;   soluble  in  hydrochloric  acid. 

Urals,  France,  Arizona. 


FIG.  1 66. — Azurite  crys- 
tal, showing  also  position 
of  optic  axes  and  axial 
plane. 


CLASS  VII.     SILICATES 

The  carbonates  are  a  very  important  group  of  oxygen  salts,  as  we 
have  just  seen,  but  the  silicates  are  even  more  important,  especially 
if  we  consider  their  number  of  species  and  their  quantity.  Their 
quantity  is  so  great  that  they  constitute  nine-tenths  of  the  mass  of 
the  earth's  crust.  There  are  several  hundred  species,  from  which  we 
select  about  forty  only.  These  forty  are  most  worthy  of  our  atten- 
tion because  of  perfection  of  form,  beauty  of  color,  durability,  utility, 
or  abundance.  Some  of  them  are  so  abundant  as  to  be  the  chief 
minerals  in  great  mountain  chains.  Some  are  highly  prized  as  gems, 
others  as  minerals  useful  for  chemical  and  various  commercial  pur- 
poses. But  it  is  as  rock-forming  minerals  par  excellence  that  they 
most  strongly  bespeak  the  attention.  The  most  abundant  repre- 
sentatives of  the  section  are  the  minerals  first  to  be  considered, 
namely,  the  feldspars. 

FELDSPAR  GROUP 

Though  the  word  feldspar  was  used  by  the  Germans  as  early  as 
1750,  the  minerals  to  which  we  now  give  that  name  have  been  dis- 
tinguished for  not  much  more  than  one  hundred  years  and  have  been 
thoroughly  studied  only  within  the  last  seventy-five  years.  Today 
no  minerals  are  better  described  and  understood.  Their  investiga- 
tion has  contributed  largely  to  the  science  of  mineralogy.  They 
deserve  the  attention  which  they  have  received,  both  because  of 
their  scientific  and  because  of  their  commercial  importance. 

They  afford  excellent  illustration  of  the  relation  of  crystal  structure 
to  physical  properties,  such  as  the  transmission  of  light  and  heat,  and 
form  an  important  feature  in  the  classification  of  igneous  rocks. 
Commercially  they  are  of  importance  because  of  their  use  in  manu- 
facture and  agriculture.  They  are  the  source  of  clay — a  mineral  sub- 
stance valuable  in  soils;  useful  for  paving  and  building  brick,  porcelain 
and  china;  and  essential  to  the  artist  and  artificer  for  modeling,  to 
the  manufacture  of  woolens  as  fuller's  earth,  and  to  the  chemist  and 
smelter  as  fire  clay. 

132 


SILICATES  133 

They  are  found  in  nearly  all  parts  of  the  country,  but  are  most 
characteristic  of  mountain  regions  and  of  areas  covered  by  glacial 
drift.  For  this  reason  the  southern  Mississippi  Valley  is  about  the 
only  portion  of  the  country  in  which  feldspar  may  rarely  be  found. 
All  of  the  feldspars  in  Illinois  are  found  in  the  drift  which  covers  the 
larger  part  of  the  state.  For  the  best  specimens  one  turns  to  igneous 
rocks  in  mountain  regions. 

All  of  the  feldspars  are  aluminium  silicates  of  potassium,  sodium, 
or  calcium,  and  rarely  barium.  Their  prevailing  color  is  white  or 
light  shades  of  red;  they  are  about  2  .5  in  specific  gravity,  6  in  hard- 
ness, and  split  readily  in  two  directions.  They  are  divided  into 
two  sections  because  some  of  them  crystallize  apparently  in  the  mon- 
oclinic  system  and  others  in  the  triclinic  system. 

The  most  important  feldspar  with  the  monoclinic  habit  is  ortho- 
clase. 

THE  ORTHOCLASES 

Orthoclase 

This  is  a  potassium  feldspar  (KAlSi3Og)  in  which  a  little  of  the 
potassium  may  be  replaced  by  sodium.  The  color  of  orthoclase 
varies  from  colorless,  glassy  adularia  and  sanidine  (No.  3477)  to 
white,  gray,  yellowish,  or  reddish  individuals  (Nos.  3413  to  3415),  or 
masses  more  or  less  opaque  owing  to  partial  conversion  into  kaolin. 

Orthoclase  is  insoluble  in  acids  without  previous  fusion.  Pure 
orthoclase  fuses  at  5  in  the  scale  of  fusibility  (about  1150°  C.),but 
with  the  increase  of  sodium,  which  is  probably  due  to  an  intermixture 
of  a  sodium  feldspar  like  albite,  the  melting-point  is  lowered. 

Orthoclase  is  the  chief  constituent  of  the  granitic  rocks  which 
occur  in  such  great  masses  in  the  Rocky  Mountains,  the  Alps,  and 
other  mountain  regions.  When  mingled  with  the  quartz  and  mica 
which  constitute  a  large  part  of  granite,  the  crystal  outlines  of  ortho- 
clase may  be  undeveloped,  but  may  still  be  readily  recognized  by  the 
cleavage  planes  which  are  parallel  to  the  base  (ooi)  and  clinopinacoid 
(oio)  and  are  at  right  angles  to  each  other.  The  quartz  in  granite  is 
without  cleavage  and  the  mica  cleaves  in  one  direction  only  and  is 
elastic. 

When  the  orthoclase  is  in  druses  (cavities  lined  with  crystals), 
well-developed  forms  like  those  in  Figure  167  show  its  pronounced 


134 


GUIDE  TO  MINERAL  COLLECTIONS 


FIG.  167. — Model  of  an  orthoclase 
crystal. 


021 


m 

FIG.  1 68.— Orthoclase 


OOI 


I  10 


FIG.  169. — Adularia  orthoclase 


110 


FIG.  171. — Baveno  twin,  composition 
face  (021). 

Oil 


OZI 

"'         ~T,r 

FIG.  170. — Model  of  Carlsbad  twin, 
interpenetrating   parallel  (oio);    twin-          FIG.  172. —Manebach  twin,  composi- 
ning  axis  c.  tion  face  (601). 


SILICATES 


135 


tendency  to  assume  clearly  marked  outlines.  Such  crystals  are 
found  abundantly  in  Colorado  and  are  composed  of  prisms  (no), 
brachypinacoids  (oio),  domes  (201),  and  basal  planes  (ooi).  The 
dome  (201)  is  nearly  at  right  angles  to  the  base.  Quite  similar  to 
them  in  shape  but  usually  thinner,  in  board  like  forms  parallel  to 
(oio),  is  sandidine  (from  aavis,  "a  table"),  which  is  found  as  limpid 
glassy  crystals  in  the  feldspar  blocks  thrown  out  of  Vesuvius  and  as 
large,  dull-gray  crystals  in  trachyte  at  the  Drachenfels,  Germany. 

Forms  less  columnar  but  elongated  in  the  direction  of  the  edge 
between  the  base  and  clinopinacoid  and  having  in  addition  pyramid 
planes  (in)  and  clinodomes  (021)  (Fig.  168)  are  customary  in  the  pink 
feldspar    of    the    Baveno 
granite  quarries. 

Glassy  crystals,  called 
adularia  from  Adula,  the 
old  name  of  St.  Gothard, 
Switzerland,  where  they 
are  found  in  abundance, 
have  the  form  shown  in 
Figure  169.  In  all  these 
crystals  the  cleavage  par- 
allel to  (ooi)  is  most  per- 
feet,  that  parallel  to  (oio) 
is  but  little  inferior,  while 
that  parallel  to  (no), 
though  barely  evident,  is 
important  in  the  orienta- 
tion of  the  crystal.  When 
prismatic  cleavage  lines 

are  placed  vertically  and  the  basal  plane  turned  until  it  slants  down- 
ward toward  the  observer,  the  crystal  is  in  conventional  position. 
The  clinopinacoid  is  almost  always  vertically  striated.  Cleavage 
cracks  on  (ooi)  often  produce  a  pearly  luster.  The  pale-blue  opal- 
escence  of  the  Ceylon  "moonstone"  is  due  to  cleavage  cracks,  to 
inclusion  of  feldspathic  material,  or  to  decomposition. 

Twinned  crystals  are  as  abundant  as  are  simple  forms,  and  the 
twinning  follows  three  laws  which  have  been  named  after  three 
localities  where  multitudes  of  good  specimens  are  found  and  were 


100 


AP 


FIG.  173. — Orthoclase  section  parallel  to  (oio); 
axial  plane,  angle  of  extinction. 


i36 


GUIDE  TO  MINERAL  COLLECTIONS 


first  studied.     The  localities  are  Carlsbad,  Bohemia;  Baveno,  Pied- 
mont, northwestern  Italy;  and  Manebach,  Saxe-Gotha,  Germany. 

Carlsbad  law:  Two  individuals  interpenetrate  parallel  to  (oio), 
one  of  them  being  turned  around  on  the  c  axis  until  the  back  side  is 
toward  the  front  (Fig.  170).  The  twinning  axis  is  c  and  the  com- 
position face  is  (oio).  If  the  crystal  is  terminated  by  (101)  and 
(ooi)  instead  of  (101)  only,  the  two  planes  will  be  nearly  in  the 
same  plane  but  may  be  distinguished,  since  the  base  is  a  plane  of 
cleavage  while  the  dome  is  not.  Also  while  the  base  is  smooth  and 
bright,  the  dome  may  be  dull. 


FIG.      174. — Orthoclase      (adularia);          FIG.  175. — Orthoclase;   positive  and 
axial  plane.  negative    direction    of    extinction    on 

(ooi)  and  (oio). 

Baveno  law :  Two  individuals  are  united  parallel  to  the  clinodome 
(021)  and  one  is  revolved  180°  so  that  the  original  back  planes  are 
turned  toward  the  front.  Twinning  and  composition  plane  is  (021). 
Since  the  angle  formed  by  (021)  and  (ooi)  is  of  nearly  45°  and 
that  between  (021)  and  (oio)  is  the  same,  Baveno  twins  may  appear 
to  be  rectangular  prisms  (Fig.  171).  But  cleavage  planes  will  show 
that  two  basal  planes  (ooi)  come  together  on  one  edge  and  two  clino- 
pinacoids  (oio)  on  the  other.  At  the  ends  will  be  observed  a  diagonal 
line  of  union.  At  one  end  are  small  salient  angles  formed  between 
(201)  and  (201)  (i3°42')  and  between  (no)  and  (110)  (io°34/).  At 


PLATE  XXVI 


a,  Microcline,  "Amazon  Stone,"  Pike's  Peak,  Colorado 


b  Microcline,  Pike's  Peak,  Colorado 


SILICATES  137 

the  other  end  are  re-entering  angles.     Baveno  cwms  are  often  repeated 
to  produce  quartets. 

Manebach  law:  Two  individuals  are  twinned  and  composed  on 
(ooi).  The  two  clinopinacoids  then  fall  in  the  same  plane,  but  the 
end  discloses  the  twinning  (Fig.  172). 

SUMMARY 

Orthoclase.— KA\SizO&;  K2O=i6.9  per  cent,  Al2O3=i8.5  per  cent, 
Si02  =  64.6  per  cent.  Monoclinic;  a:b:c=o. 658: 1:0.555.  /3=ii6°  3'- 
(no),  (ooi),  (oio),  (101),  (201),  (021),  (in).  Carlsbad  law,  twinning 
axis  c:  composition  plane  (oio).  Baveno  law,  twinning  plane  and  composi- 
tion plane  (021).  Manebach  law,  twinning  plane  and  composition  plane 
(ooi).  Cleavage  parallel  (ooi),  (oio)  perfect,  (no)  imperfect.  Brittle; 
fracture  conchoidal. 

Hardness  =  6;  gravity  =2. 5.  Colorless  to  red;  vitreous;  transparent; 
18=1.524;  double  refraction  negative,  weak;  y— a  =  o.oo6.  Axial  plane 
perpendicular  to  (oio) .  Acute  bisectrix  5°,  above  a  axis  on  (100) :  extinction 
on  (oio)  — 5°,  on  (ooi)  o°.  2  E  varies  but  usually  is  in  the  neighborhood 
of  120°. 

Insoluble;  fusible  (5). 

In  granite,  gneiss,  trachyte.  More  common  in  metamorphic  rocks 
than  are  plagioclases.  Mountain  regions,  Colorado,  Switzerland,  Italy; 
confined  to  the  drift  in  Illinois. 

Microcline 

Closely  related  to  orthoclase  and  connecting  it  crystallographi- 
cally  with plagioclase  is  microcline.  In  orthoclase  (opdos,  "straight"; 
/cXdco,  "to.  cleave")  the  basal  plane  and  cleavage  parallel  to  it 
form  a  right  angle  to  the  clinopinacoid  plane  and  the  cleavage 
parallel  to  it.  In  microcline  (/tiucpfo,  "small";  K\iveiv,  "to  incline") 
these  planes  deviate  but  about  15'  to  35'  from  a  right  angle;  that  is, 
the  angle  which  (ooi)  makes  with  (oio)  is  generally  about  89°  30'. 
In  plagioclase  (TrXcryios,  "oblique";  /cXdco,  "to  cleave")  the  angle 
between  the  basal  plane  (ooi)  and  brachypinacoid  (oio)  is  about  86°. 

The  chemical  composition,  hardness,  specific  gravity,  and  general 
character  of  microcline  (No.  3418)  are  the  same  as  those  of  ortho- 
clase, and  were  it  not  for  the  inclination  of  the  b  axis  to  the  c  the 
two  species  would  be  classed  as  one.  But  because  of  their  inclina- 
tion microcline  is  a  triclinic  feldspar.  Its  crystals  are  generally  com- 
posed of  two  sets  of  twins,  one  parallel  to  the  brachypinacoid  (oio) 


138  GUIDE  TO  MINERAL  COLLECTIONS 

and  the  other  at  right  angles  to  it,  namely,  parallel  to  the  edge 
formed  by  (ooi),  the  base,  and  (101),  the  macrodome.  This  produces 
a  curious  cross-hatching  or  grating  structure  best  seen  under  the 
microscope  when  the  nicols  are  crossed  as  two  series  of  lamellae  in 
the  basal  plane.  It  is  called  the  "microcline  structure."  It  would 
be  possible  for  the  twins  which  cause  the  cross-hatching  to  be  so  fine 
as  to  be  invisible.  Then  the  inclination  of  (ooi)  to  (oio)  might 
disappear,  the  cross-hatching  become  indistinguishable,  and  micro- 
cline then  resemble  orthoclase  completely.  For  this  reason  some 
authors  think  that  orthoclase  is  simply  an  extreme  form  of  microcline 
and  that  all  of  the  feldspars  are  triclinic. 

Green  varieties  of  microcline  are  called  Amazon  stone.  Pike's 
Peak,  Colorado  (Nos.  3416,  3245,  3420,  and  1251),  and  the  Ilmen 
Mountains  in  Russia  have  long  been  reputed  for  fine  specimens  of 
Amazon  stone  which  they  have  furnished.  Museums  are  quite 
generally  supplied  with  specimens  from  these  localities. 

SUMMARY 

Microcline.  —  Like  orthoclase,  except  that  the  b  axis  is  inclined  about 
half  a  degree,  the  basal  cleavage  often  shows  fine  striations  and  between 
crossed  nicols  cross-hatching,  and  the  angle  of  extinction  on  base  is  +15°  30', 
while  in  orthoclase  it  is  o°. 

Anorthoclase.  —  (Na,K)AlSi3O8.  Triclinic;  resembles  microcline.  Cross- 
hatching  often  so  fine  as  to  be  scarcely  visible;  (201)  and  (no)  often 
elongated. 

In  alkaline  lavas  (Pantellaria)  and  porphyries  (Christiania). 


Hyalophane.  —  KaBaALiSigO^.  A  double  salt  composed  of  two  molecules 
of  orthoclase  (KAlSi3Os)  and  one  of  barium  alumino-silicate  (BaAl2Si2O8). 
It  occurs  in  monoclinic  glassy  crystals  which  closely  resemble  adularia 
(Fig.  174).  ,,.  ^ 

In  dolomite  in  Tyrol,  etc. 


Of  the  more  than  threescore  minerals  thus  far  considered,  but 
one  before  microcline  has  been  found  to  crystallize  in  the  triclinic 
system,  and  that  one,  cryolite,  is  so  poor  a  representative  of  the 
system  that  no  description  of  triclinic  symmetry  was  given  in  that 
connection.  But  microcline,  and  more  especially  the  plagioclases 
now  about  to  be  described,  are  the  most  important  minerals  con- 
structed with  triclinic  symmetry. 


SILICATES 


139 


In  the  triclinic  system  are  grouped  such  forms  as  have  three 
axes  of  unequal  lengths  crossing  each  other  at  angles  not  right  angles. 

The  angle  between  c  and  b  is  called  a,  that  between  c  and  a,  /3, 
and  that  between  a  and  b,  7,  as  indicated  in  Figure  176.  Upon 
these  axes  planes  are  constructed  which  cut  all  three  axes,  pyramid 
planes  (in);  or  which  cut  two  axes  and  are  parallel  to  the  third, 
prisms  (no)  and  domes  (on),  (100);  or 
which  cut  one  axis  and  are  parallel  to 
two,  pinacoids  (oio),  (100),  (ooi).  The 
longer  of  the  two  lateral  axes  is  chosen 
as  b  and  the  dome  and  pinacoid  parallel 
to  it  are  the  macrodome  and  macro- 
pinacoid.  The  brachydome  and  pina- 
coid are  parallel  to  a.  The  figures 
produced  by  any  one  kind  of  plane  'are 
not  closed  forms.  They  have  neither 
planes  nor  axes  of  symmetry  but  a 
center  of  symmetry  only.  The  figures 
may  readily  be  drawn  by  following  the 
method  employed  for  preceding  systems. 
This  system  is  the  sixth  and  completes 
the  crystallographic  groups  which  embrace  all  crystallized  minerals. 


FIG.  176. — Triclinic  axes  of 
copper  sulphate;  no  axes  at 
right  angles. 


THE  PLAGIOCLASES 

The  feldspars  which  exhibit  between  the  two  chief  cleavage  planes 
angles  markedly  different  from  a  right  angle  are  grouped  together  as 
plagioclases.  They  compose  two  species  widely  separated  chemically, 
one  being  the  sodium  feldspar,  albite  (NaAlSijOg),  and  the  other  the 
lime  feldspar,  anorthite  (CaAl2Si2O8).  Between  these  two  is  a  series 
formed  by  insomorphous  mixtures  of  albite  and  anorthite  molecules 
in  varying  proportion.  If  Ab  represents  the  albite  molecule  and  An 
the  anorthite  molecule,  the  typical  composition  of  the  chief  varieties 
may  be  expressed  as  follows: 

Albite  ;v      Ab 

Oligoclase  Ab3  An 

Andesine  Ab  An 

Labradorite  Ab  An3 

Bytownite  Ab  Am 

Anorthite  An 


140 


GUIDE  TO  MINERAL  COLLECTIONS 


In  physical  as  well  as  chemical  properties  these  six  minerals  form 
a  continuous  series  and  afford  a  fine  illustration  of  the  variations  of 
optical  characters  with  molecular  constitution.  They  may  readily 
be  distinguished  from  each  other  by  microscopic  or  by  chemical 
tests. 

Plagioclase  strongly  resembles  orthoclase  in  crystallographic  and 
physical  properties,  but  may  usually  be  recognized  by  the  fine  stri- 
ations  on  the  basal  plane.  These  striations  are  due  to  repeated 
twinning  of  thin  leaves  parallel  to  the  brachypinacoid  (oio). 

Some  plagioclases  are  more  common  than  orthoclase  in  igneous 
rocks,  both  as  constituent  of  the  ground  mass  and  as  inclosed  crystals 
(phenocrysts).  The  six  different  kinds  are  shown  in  their  order, 
beginning  with  albite. 

Albite 

Albite  (albus,  "white")  occurs  in  white  masses  or  as  crystals  in 
cavities  in  igneous  rocks  and  crystalline  schists  in  the  Appalachian 
(No.  3 1 24)  and  Cordilleran  regions 
and  in  all  the  mountain  ranges  of 
the  world. 


FIG.  178. — Albite  twinned  on  (oio); 
albite  law. 


The  simple  crystal  (Fig.  177)  resembles  orthoclase  in  outline,  as 
do  also  some  of  the  twins  which  follow  the  Carlsbad,  Baveno,  and 
Manebach  laws.  But  the  most  common  and  typical  crystals  are 
twinned  according  to  the  albite  and  the  pericline  laws. 

According  to  the  albite  law  the  twinning  plane  and  the  composi- 
tion face  are  (oio)  and  the  basal  planes  form  re-entrant  angles  with 
each  other  (Fig.  178).  The  different  crystals  are  usually  thin  as 


SILICATES 


141 


paper  and  repeated  so  as  to  produce  polysynthetic  twins  which  give 
rise  to  fine  striations  and  pearly  luster  best  seen  on  the  basal  plane. 

According  to  the  pericline  law 
(IIepLK\ivr)s,  "  sloping,"  so  called 
because  of  the  oblique  appearance 
of  the  crystals  which  are  often 
elongated  parallel  to  the  b  axis) 
(Fig.  179),  the  b  axis  is  the 
twinning  axis  and  the  twin  crys- 
tals are  united  along  a  face  called 
the  rhombic  section,  which  is 
parallel  to  b  but  slopes  backward 
forming  an  angle  of  27°  with 


201 


FIG.   179. — Albite,  pericline  twin 


FIG.  180.— Albite,  (ooi),  (oio),  (no), 
(ioT);  axial  plane. 


oio 


100 


FIG.  181. — Albite  section  parallel  (100)      FIG.  182. — Albite  section  parallel  (oio) 


the  edge  (ooi)  and  (oio).     The  portions  of  (oio)  above  and  below 
the  line  of  union  form  an  angle  with  each  other. 


142 


GUIDE  TO  MINERAL  COLLECTIONS 


Albite  resembles  orthoclase  in  hardness  and  fusibility  but  is 
heavier  and  may  readily  be  distinguished  by  use  of  a  heavy  liquid 
like  methylene  iodide  (sp.  gr.  =  3  .3). 

It  often  incloses  minerals  prized  as  gems,  such  as  the  phenacite, 
topaz,  tourmaline,  and  beryl  of  the  Urals,  Ilmen,  and  Rocky  Moun- 
tains. 

SUMMARY 

Albite. — NaAlSijOg;  Na2O=n.8  per  cent,  Al2O3=i9.5  per  cent, 
SiO2  =  68.7  per  cent.  Triclinic;  symmetry  holosymmetric;  a:b:c= 
0.6335:1:0.5577.  a  =  94°3',  (3=n6°  29',  y  =  88°  9'.  (no),  (oio),  (ooi), 
(201),  (ni).  Common  twins;  twinning  plane  and  composition  face  (oio) 
for  albite  law;  axis  b  is  the  twinning  axis  and  the  rhombic  section  the 
composition  plane  for  pericline  law.  Cleavage  (ooi) ,  perfect;  (oio) ,  (i  10) , 
imperfect;  brittle;  fracture  uneven. 

Hardness=6;  gravity  =2. 63.  Colorless;  vitreous,  transparent;  ft= 
I-533-  Double  refraction  positive,  weak;  y— a  =  o.on.  Acute  bisectrix 
c  in  zone  (oio) :  (ooi)  inclined  at  16°  to  the  perpendicular  of  (ooi) .  Obtuse 
bisectrix  a  inclined  at  70°  to  the  perpendicular  of  (ooi).  Red  light  less 
dispersed  than  violet  (p<v). 

Insoluble ;  fusible  at  4. 

Rocky  Mountains,  Ural  Mountains,  etc. 

Anorthite 

The  plagioclase  farthest  removed  from  albite  in  composition  and 
physical  character  is  the  comparatively  rare  mineral  anorthite 
(CaAl2Si2Og)  found  in  basalt  in 
Japan,  in  limestone  and  augitic 
blocks  ejected  from  Vesuvius,  etc. 
The  crystals  are  limpid  glassy 
forms  exhibiting  a  larger  number 


FIG.  183. — Rhombic  section  of  an- 
orthite. 


FIG.  184. — Anorthite,  showing  posi- 
tion of  axial  plane  and  bisectrix. 


SILICATES  143 

of  faces  than  albite  and  having  less  marked  stria tions  on  the 
brachypinacoid.  The  optical  properties  are  very  different  from 
those  of  albite,  as  may  be  seen  in  the  table  (p.  144).  Carlsbad, 
Manebach,  pericline,  and  albite  laws  of  twinning  are  exhibited. 
When  twinned  according  to  the  pericline  law  the  rhombic  section 
slopes  down  forward  from  the  basal  plane  (Fig.  183).  Such  a  direc- 
tion of  slope  is  called  negative;  the  backward  slope  such  as  that 
shown  by  albite  is  called  positive. 

Anorthite  is  heavier  than  albite  and  more  difficultly  fusible  (5), 
but  more  easily  soluble. 

SUMMARY 

Anorthite. — CaALSiaOg;  CaO  =  2o.i2  per  cent,  A12O3=36.72  per  cent, 
Si02  =  43.i6  per  cent.  Triclinic;  symmetry  holosymmetric ;  a:b:c= 
0.6347:1:0.5501.  a  =  Q3°  13',  /?=ii5°  55',  7  =  91°  12'.  (no),  (oio), 
(ooi),  (100),  (101),  (201),  (021),  (023),  (in),  (iii),  (iii),  (207),  (130). 
Twinned  according  to  Carlsbad,  Baveno,  Manebach,  albite,  and  pericline 
laws.  Cleavage  (oo i ),  perfect;  (oio),  fair.  Brittle;  fracture  conchoidal. 

Hardness  =  6. 5;  gravity  =2. 7  5.  Colorless;  vitreous;  transparent; 
/8=i.58.  Double  refraction  weak,  negative;  y— a=o.oi3.  Obtuse 
bisectrix  y  perpendicular  to  (021).  Acute  bisectrix  (a)  inclined  inside 
the  crystal  at  53°  14'  to  the  normal  of  (ooi),  at  58°  to  normal  of  (oio),  at 
16°  52'  to  normal  of  (ni). 

Decomposed  by  hydrochloric  acid;  fusible  at  5. 

Vesuvius,  Japan. 

INTERMEDIATE  PLAGIOCLASES 

Oligoclase,  andesine,  labradorite,  and  bytownite  are  usually 
found  as  rock  constituents  in  massive  or  microscopic  forms  lacking 
well-defined  faces.  Chemical  or  optical  tests  are  necessary  to  dis- 
tinguish these  plagioclases  from  each  other. 

Oligoclase  (soda  lime  feldspar)  is  found  as  grayish-white,  trans- 
lucent, somewhat  greasy-looking  masses  with  orthoclase  in  granite 
(No.  3422).  The  striations  on  the  basal  planes  aid  in  distinguishing 
it  from  the  orthoclase.  Reddish  cleavable  masses  with  a  golden 
shimmer  due  to  spangles  of  hematite  or  goethite  are  called  "adven- 
turine  feldspar"  (Nos.  3423,  3424)  or  "sunstone." 

Labradorite  (lime  soda  feldspar),  found  abundantly  in  Labrador 
(Nos.  3425,  3427,  3428),  the  Adirondacks,  and  Wichita  Mountains, 


144 


GUIDE  TO  MINERAL  COLLECTIONS 


occurs  in  dark  cleavable  masses,  commonly  iridescent,  and  showing 
beautiful  red,  yellow,  and  green  colors.  The  colors  are  due  partly  to 
interference  effects  caused  by  twinning  lamellae  and  partly  to  inclu- 
sions of  hematite,  goethite,  or  diallage.  Labradorite  is  notably 
absent  in  rocks  containing  orthoclase  and  quartz,  but  is  characteristic 
of  basic  rocks  like  gabbro  and  dolerite. 

Often  associated  with  the  labradorite  is  another  iridescent 
mineral,  hypersthene.  The  rock  formed  chiefly  of  these  two  minerals 
is  called  "labrador  spar"  and  is  used  extensively  in  decorative  work. 
The  finest  church  in  Moscow  (St.  Savior),  with  capacity  for  seven 
thousand  worshipers  at  one  time,  is  wainscoted  with  beautiful 
chatoyant  labradorite. 


CHEMICAL  CHARACTERISTICS  AND   SPECIFIC   GRAVITY  OF 
THE  FELDSPARS 


Composition 

SiO, 

AUO, 

K,0 

Na,O 

CaO 

Specific 
Gravity 

Orthoclase  

KAlSi3O8 

64.6 

18.4 

l6.Q 

2    «?6 

Microcline  

64.6 

^•5" 
2  «;6 

Anorthoclase 

NaRAlSijOs 

Albite 

NaAlSi3O8 

68  7 

10    ^ 

ii  8 

o 

2    62 

Oligoclase 

Ab3An 

62  o 

24  o 

8  7 

5-1 

2    6< 

Andesine 

AbAn 

ce   6 

28  3 

r    7 

IO   4 

^.u^> 
2    60 

Labradorite     

AbAn3 

40   3 

•3,2    6 

2    8 

IIT    7 

2    72 

Bytownite       

AbAne 

46  6 

34  4 

i  6 

17   4 

2    74 

Anorthite  

CaAl2Si2Os 

43    2 

36.7 

o. 

2O   I 

2    7<C 

CRYSTALLOGRAPHIC  CHARACTERISTICS  OF  THE 
FELDSPARS 


Axes 

Angle  between  Axes 

Extinc- 
tion on 

001 

Extinc- 
tion on 

010 

Mean 
Refrac- 
tion 
0 

Rhombic 
Section 
Angle  | 

a:    b:    c 

a 

0 

7 

Orthoclase  
Microcline  .  .  . 
Anorthoclase  . 

.  0.658:  :o.555 
0.658:  :o.555 

90° 

89°3o' 

ii6°3' 

9o° 

90° 

°o°', 

K 

•523 
.526 

Albite  

0.633:  :o.557 
0.632:  :o.552 
0.635:  10.552 
0.637:  :o.5S4 

93°23' 
93°3i/ 

Il6°29' 

Il6X 
ii6Y 

88V 
89X 

4°30' 

iv, 

o  .    / 

37° 

19° 

i6°3 

20*28; 

36°29 

•534 

•542 

•570 
1.582 

1 

16° 

Oligoclase  
Andesine  
Labradorite..  . 
Bytownite  .... 

Anorthite  .... 

0.634:1:0.550 

93°i5' 

»S°5S' 

9I°I2' 

SILICATES 


145 


m 


FIG.  185. — Microscopic 
section  of  leucite  between 
crossed  nicols. 


Leucite 

Leucite  (A.CVKOS,  "white")  crystallizes  in  white,  round  crystals 
(Fig.  7)  from  an  inch  in  diameter  to  forms  microscopic  in  size  in 
igneous  rocks,  such  as  those  found  in  the  Leucite  Hills,  southwestern 
Wyoming,  and  at  Mount  Vesuvius  (No.  3244). 

When  leucite  assumes  its  definite  form  at  temperatures  above 
500°  the  crystals  are  trapezohedrons,  but  at  ordinary  temperatures, 
while  the  external  form  remains  the  same,  the  internal  condition  is 
that    of    the    orthorhombic    system.      The 
microscope  reveals  multitudes  of  fine  layers 
which  cross  each  other  at  right  angles,  and 
occasionally  groups  diagonal  to  these  (Fig. 
185).     These  layers  have  the  optical  prop- 
erties   characteristic    of    the    orthorhombic 
system.     Hence  leucite  is  said  to  be  pseudo- 
regular.      Externally   it   is   always   regular, 
internally    under   ordinary   conditions  it  is 
orthorhombic.     Crystals  microscopic  in  size 
are  often  free  from  the  orthorhombic  layers. 

Furthermore,  inclusions  of  other  minerals,  such  as  augite,  olivene, 
and  apatite,  are  arranged  parallel  to  trapezohedral  faces — an  addi- 
tional indication  that  the  mineral  swings  between  the  orthorhombic 
and  the  regular  system.  Its  instability  is  further  shown  by  the  fact 
that  in  nature  it  is  usually  white  and  opaque,  owing  to  its  change 
into  analcite,  mica,  or  kaolin. 

SUMMARY 

Leucite. — KAl(SiO3)2;  K2O=2i.58  per  cent,  A12O2=23.4O  per  cent, 
SiO2=55.o2  per  cent.  Orthorhombic  (211).  At  ordinary  temperature 
all  but  microscopic  crystals  contain  fine  orthorhombic  lamellae  which  are 
weakly  doubly  refracting.  Cleavage  parallel  (no)  imperfect;  brittle; 
fracture  conchoidal. 

Hardness  =  5 . 5 ;  gravity  =2. 5.  Colorless;  vitreous;  transparent; 
£=1.508. 

Infusible;  soluble  in  hydrochloric  acid. 

Vesuvius,  Eifel,  Wyoming. 

PYROXENE  GROUP 

Hardly  less  abundant  than  the  white  feldspars  as  rock  constitu- 
ents are  the  colored  pyroxenes.  The  name  pyroxene  (irvp, 


146  GUIDE  TO  MINERAL  COLLECTIONS 

"a  stranger  to  fire")  was  given  by  Hauy  to  certain  green  crystals 
found  in  Italian  lavas,  with  the  thought  that  they  were  only  acci- 
dentally present,  having  been  caught  up  while  the  lava  was  passing 
surrounding  rock.  Now  it  is  known  that  they  are  essential  con- 
stituents of  many  igneous  rocks  and  are  as  much  misnamed  as  is  a 
white  blackbird!  According  to  their  crystallography,  they  are 
classified  in  three  sections,  the  orthorhombic,  the  monoclinic,  and 
the  triclinic.  Most  prominent  in  the  first  section  are 

ORTHORHOMBIC  PYROXENES 
Enstatite  and  Hypersthene 

Enstatite  is  a  white,  green,  or  brownish  mineral  occurring  rarely 
in  columnar,  orthorhombic  crystals,  and  commonly  in  fibrous,  silky, 
opaque  masses.  Measurable  crystals  were  found  by  von  Lang  in 
1871  in  a  meteorite  which  fell  in  Bohemia,  and  three  years  later  cer- 
tain large  crystals  contained  in  Norwegian  schists  were  found  to  be 
enstatite  by  Brogger.  Chemically  enstatite  is  a  magnesium  silicate 
(MgSiO3).  The  presence  of  iron  often  gives  a  metallic  luster  (bronz- 
ite).  When  iron  replaces  a  large  part  of  the  magnesium,  a  some- 
what darker,  heavier,  and  more  soluble  mineral,  hypers thene,  results. 

When  a  thin  section  of  either  of  these  minerals  cut  parallel  to  the 
prism  or  brachypinacoid  plane  is  viewed  under  a  microscope  between 
crossed  nicols,  it  becomes  dark  if  the  crystal  axes  are  parallel  to  the 
cross-hairs  of  the  microscope,  as  is  characteristic  of  an  orthorhombic 
mineral.  The  extinction  is  said  to  be  parallel.  Further,  these 
pyroxenes  change  from  reddish-brown  to  green  according  to  the 
direction  in  which  a  thin  section  is  viewed  under  the  microscope. 
That  is,  they  are  strongly  pleochroic,  and  this  property  aids  in  dis- 
tinguishing them  from  the  pyroxenes  next  to  be  studied. 

Both  enstatite  and  hypersthene  are  found  in  granular  eruptive 
rocks  and  schists  such  as  are  common  in  most  mountain  regions. 

SUMMARY 

Enstatite.— MgSi03;  MgO=4o  per  cent,  SiO2=6o  per  cent.  Ortho- 
rhombic;  a:6:c=o. 97:1:0. 57.  (no):(iio)  =  88°  20'.  Cleavage  parallel 
(no),  (oio).  Brittle;  fracture  even. 

Hardness=  5.5;  gravity = 3 . 2.  White,  green,  brown ;  vitreous;  trans- 
lucent; mean  refraction  /8=  1.659.  Double  refraction  weak,  positive; 
y— a=o.oo9.  Axial  plane  (oio);  acute  bisectrix,  normal  to  (ooi), 
2H  =  79°;  p<v. 


SILICATES 


147 


Infusible,  named  after  CI/O-TCIT^S,  "opponent,"  because  so  refractory. 
Insoluble ;   with  cobalt  turns  pink.    Decomposes  into  serpentine  and  talc. 
New  York,  Norway,  Germany.     Common  in  meteorites. 

Hypersthene. — (MgFe)SiO3;  MgO  from  26  to  n  per  cent,  FeO  from 
10  to  34  per  cent.  Agrees  .with  enstatite  except  as  follows: 

Gravity =3. 4.  Dark  green  to  black.  (3=  1.702.  Double  refraction 
weak,  negative;  y— a  =  0.013.  Acute  bisectrix  normal  to  (100).  Dis- 
persion p>v. 

.  Fusible  to  magnetic  mass.     Partly  soluble  in  hydrochloric  acid. 

Common  with  labradorite  in  granular  eruptive  rocks  in  Labrador. 
Greenland,  Norway,  New  York. 

MONOCLINIC  PYROXENES 


The  monoclinic  section  of  py- 
roxenes is  more  important  than 
either  the  orthorhombic,  already 
considered,  or  the  triclinic,  which 
will  be  studied  later.  The  chief 
monoclinic  pyroxenes  are 

Diopside  and  Augite 

These  two  minerals  occur  in 
short,  stout,  green  to  black  crys- 
tals in  igneous  rocks,  and  are 
nearly  as  abundant  as  is  the 
feldspar  in  these  rocks  (Nos.  3676, 
3677,3680). 

Diopside  (Nos.  3429  and  3430) 
is  clear  pale  green  in  color.  Some- 
times a  crystal  is  darker  at  one 


to? 

FIG.  1 86a.— Diopside 


FIG.  1866. — Photograph  of  diopside 
from  Cantley,  Quebec,  Canada:  (in), 
(100),  (101),  (no),  (100),  (oio);  about 
1 2  inches  long. 


J48 


GUIDE  TO  MINERAL  COLLECTIONS 


end  than  at  the  other,  and  also  differently  terminated  at  the 
opposite  ends.  The  usual  shape  of  the  crystal  is  illustrated  in 
Figures  186-88.  In  composition  diopside  is  a  silicate  of  calcium 
and  magnesium,  CaMg(SiO3)2. 


01° 


10) 


110 


FIG.  187. — Diopside 


FIG.   188. — Diopside,  showing  optic 
axes,  acute  bisectrix,  axes  of  elasticity » 


Hi 

\ 


100 


A 


no 


.010 


100 


110 


_.oio 


FIG.  189. — Augite 


FIG.  190. — Augite  twin  parallel  to  (100) 


Augite  is  dark  green  or  black  (No.  343 1)»  Tne  crystals  are 
usually  terminated  with  pyramidal  planes,  while  prism  and  pinacoid 
planes  are  both  well  developed.  Twins  parallel  to  the  orthopinacoid 
are  common  (Figs.  189  and  190). 


SILICATES 


149 


While  iron  is  usually  present  in  both  diopside  and  augite,  it  is 
more  abundant  in  the  latter.  Diopside  lacks  aluminum.  There- 
fore the  pyroxenes  are  often  divided  into  non-aluminous  (diopside) 
and  aluminous  (augite)  varieties. 

Light  green  or  white  diopside  is  abundant  in  crystalline  limestones 
and  dolomites.  Green  or  black  augite  is  common  in  granite  or 

eruptive  rocks  (No.  3433).  When 
black  basalt  decomposes,  augite 
crystals  sometimes  fall  out  and 
may  be  easily  collected  in  quan- 
tities. 

A  thin  section  of  augite  cut 

perpendicular  to  the  c  axis  when 
FIG.  ioi.  —  Augite  cross-section  per-  ,  ,  . 

pendicular  to  prism  planes.  ™W*d     Under     the     nucroscope 


001 


too 


FIG.  192. — Enstatite,  showing  parallel          FIG.  193. — Diopside,  showing  oblique 
extinction.  extinction  angle  of  38°. 


shows  fine  cleavage  lines  parallel  to  the  prism  planes.  These  lines 
form  an  angle  of  nearly  90°  with  each  other  and  the  outline  of  the 
figure  is  eight-sided  (Fig.  191).  The  eight-sided  outline,  the  cleavage 
angle,  and  lack  of  pleochroism  aid  in  distinguishing  augite  from  horn- 
blende. Hornblende  presents  a  six-sided  figure  with  cleavage  line 
forming  an  angle  of  124°,  and  furthermore  is  strongly  pleochroic. 

Fragments  or  thin  sections  of  the  members  of  the  pyroxene  group 
may  be  recognized  by  their  extinction  angle.    A  section  of  enstatite 


150  GUIDE  TO  MINERAL  COLLECTIONS 

cut  parallel  to  the  brachypinacoid  and  viewed  in  parallel  light 
between  crossed  nicols  becomes  dark  when  the  c  axis  is  parallel  to 
one  of  the  cross-hairs  of  the  microscope  (Fig.  192).  Diopside  when 
so  examined  must  be  turned  clockwise  about  38°  before  it  becomes 
dark  (Fig.  193).  Augite  requires  even  a  greater  angle  of  revolution, 
sometimes  being  as  large  as  54°.  In  each  case  the  angle  of  extinction 
increases  with  the  amount  of  iron  present. 

SUMMARY 


Diopside.—  CaMg(Si03)2;  CaO  =  25.g  per  cent,  MgO=i8.5  per  cent, 
SiO2=55-6percent.  Monoclinic;  a:b:c=i.  0921:1:0.  5893.  /3=io5°5o'. 
(no),  (100),  (oio),  (ooi),  (101),  (in),  (221).  Twinned  on  (100).  Cleavage 
perfect  parallel  (no),  imperfect  parallel  (100),  (oio).  Brittle;  fracture 
conchoidal. 

Hardness  =  5  .  5  ;  gravity  =3.  3.-  Light  green;  vitreous;  transparent. 
Mean  refraction  (y8)  =  i.68i,  maximum  (y)  =  1.703.  Double  refraction 
positive,  strong;  7—0  =  0.030.  Axial  plane  (oio).  Acute  bisectrix 
inclined  37°  35'  to  c  and  the  obtuse  bisectrix  inclined  below  a  in  front 
21°  45'  (Fig.  193).  Axial  angle  (2  E)  =  68°. 

Fusible;  insoluble. 

In  crystalline  limestones  and  dolomites,  both  east  and  west,  and  in 
the  drift. 


Augite.—     MgksioVj   Fe  A  is  also  always  present. 

Augite  has  nearly  the  same  character  as  diopside,  but  contains  A12O3 
and  Fe2O3  in  addition  to  calcium  and  magnesium  silicates,  and  is  darker  in 
color. 

More  readily  fusible  than  diopside. 

In  granitic  and  eruptive  rocks  the  world  over. 


Jadeite 

Jadeite  is  a  compact,  tough,  alkaline  pyroxene  having  the  compo- 
sition NaAl(SiO3)2.  It  is  7  in  hardness  and  3.3  in  specific  gravity, 
is  translucent,  and  varies  in  color  from  blue  and  green  to  white. 
When  carved  and  polished  it  has  a  soft  waxy  luster  which  is  very 
pleasing,  and  for  that  reason  it  has  been  used  for  many  hundreds 
of  years  as  material  for  carving  into  ornaments,  vases,  etc.  Being 
tough  and  hard,  it  is  very  enduring. 


SILICATES  151 

SUMMARY 

Jadeite. — NaAl(SiO3)2;  Na20=i5.4  per  cent,  A12O3=25.2  per  cent, 
SiO2=59-4  per  cent.  Monoclinic;  massive,  sometimes  granular,  slightly 
fibrous;  fracture  splintery;  very  tough. 

Hardness=y;  gravity =3. 3-.  Greenish,  bluish,  white;  waxy,  dull, 
translucent;  2  7=72°. 

Fuses  readily;  not  attacked  by  acids  after  fusion;  different  from 
saussurite. 

Burma,  Thibet,  Mexico. 

TRICLINIC  PYROXENE 

The  triclinic  pyroxene  rhodonite  (podov,  "a  rose")  is  a  beautiful 
red  mineral  which,  because  of  its  hardness  (6)  and  fine  color,  is  used 
for  ornaments  such  as  brooches,  cuff  buttons,  watch  charms,  ink- 
wells, paper  weights,  vases,  mantelpieces,  and  table  tops.  In  the  Urals 
masses  of  such  size  have  been 
found  as  to  be  available  for  tomb- 
stones. In  the  late  Czar's  lapid- 
ary shops  at  Petrograd  some  years 
ago,  the  author  saw  an  oblong 
block  of  rhodonite  7X4X3  feet 

in  size,   being  carved  for  a  sar-  ^     (    f         ^      ||o|O 

cophagus  for  royalty,  and  which 
was  valued  at  six  hundred  thou- 
sand dollars.  |0° 

When  crystals   of   rhodonite  FIG.  194 —Rhodonite 

occur,  as  is  often  the  case  in  Nor- 
way, England,  and  New  Jersey  (No.  3438),  they  are  tabular  (Fig.  194) 
in  form  or  stout  like  augite. 

Rhodonite  is  a  silicate  of  manganese  (MnSiO3)  but  usually  con- 
tains calcium,  iron,  and  in  New  Jersey  zinc. 

SUMMARY 

Rhodonite. — MnSi03;  MnO=54.i  per  cent,  Si02=45-9  per  cent. 
Triclinic;  a:b:c=i  .073:1:0.621.  a  =  103°  18', /?  =108°  44',  7  =  87°  39'. 
(no),  (oio),  (ooi),  (221).  Cleavage  (110),  (no),  perfect;  (ooi),  fair. 
Brittle;  fracture  uneven. 


152 


GUIDE  TO  MINERAL  COLLECTIONS 


Hardness=6;  gravity =3. 6.  Red;  vitreous;  translucent.  Mean 
refraction  (/?)  =  1.73.  Double  refraction  negative,  weak;  y— a  =  o.oio. 
Axial  plane  is  inclined  at  63°  to  (110)  and  38°  to  (ooi).  Acute  bisectrix 
inclined  51°  47'  to  the  normal  of  (110)  and  51°  40'  to  the  normal  of  (ooi). 
Axial  angle  (2  £0  =  79°;  p<v. 

Readily  fusible  (2.5);  partly  soluble  in  hydrochloric  acid. 

Urals,  Norway,  England,  New  Jersey. 

AMPHIBOLE  GROUP 

The  minerals  in  this  group  resemble  pyroxene  in  composition, 
color,  and  form. 

Like  the  pyroxenes  they  have  orthorhombic,  monoclinic,  and  tri- 
clinic  representatives.  The  term  amphibole  (a^0t/3o\?7,  " doubtful") 
was  given  by  Haiiy  to  replace  the  name  " schorl"  used  by  miners 
for  both  hornblendes  and  tourmaline — two  minerals  which,  though 
resembling  each  other,  are  chemically  and  crystallographically 
different.  The  readiest  means  of  distinguishing  amphiboles  from 
pyroxenes  are  the  crystal  form  and  cleavage,  as  may  be  seen  from  the 
descriptions  following. 

ORTHORHOMBIC  AMPHIBOLE 

Anthophyllite,  corresponding  to  the  orthorhombic  pyroxene, 
hypersthene,  occurs  in  brown  fibrous  or  flaky  masses  in  mica  schist 
in  Norway,  Pennsylvania  (No.  3440),  North 
Carolina,  etc.  Crystals  are  extremely  rare, 
but  under  the  microscope  it  may  be  observed 
that  cleavage  parallel  to  (oio)  is  inferior  to 
that  of  hypersthene.  Anthophyllite  is  less 
pleochroitic  than  hypersthene  but  has  greater 
double  refraction ;  7  —  a  =  o .  024. 

The  name  anthophyllite  is  derived  from 
the  Latin  word  for  clove  (anthophyllum) 
because  of  the  clove-brown  color  of  the 

mineral. 

SUMMARY 


FIG.  195. — Anthophyl- 
lite, axial  plane  and  optic 
axes. 


Anthophyllite—  (MgFe)SiO3;  MgO=  27 .8 per 
cent,  FeO=i6.6  per  cent,  SiO2  =  55.6  per  cent. 
Orthorhombic;  crystals  rare;  fine  fibers  or  flakes  common. 

Hardness=6;    gravity =3.1.    Brown  to  green,  at  times  metalloidal; 
translucent.    Mean  refraction   (ft)  =  1.642.     Double  refraction  positive; 


SILICATES  153 

y— (1  =  0.024.      Axial  plane   parallel   (oio).      Acute  bisectrix  normal  to 
(ooi). 

Difficultly  fusible;  insoluble. 

In  gneisses  and  schists  in  Norway,  Pennsylvania,  North  Carolina,  etc. 

MONOCLINC  AMPHIBOLES 

As  the  monoclinic  pyroxenes  are  the  most  abundant  and  important 
of  the  pyroxenes,  so  the  monoclinic  amphiboles  far  surpass  in 
abundance  the  orthorhombic  and  triclinic  forms.  The  white  tremolite, 
green  actinolite,  and  black  hornblende  constitute  the  chief  repre- 
sentatives of  the  monoclinic  forms. 

Tremolite 

Tremolite  corresponds  to  diopside  but  contains  more  magnesium 
and  is  usually  fibrous  or  columnar  and  without  terminating  planes. 
It  is  white  or  pale  green  in  color.  As  the  amount  of  iron  (FeO) 
increases,  it  becomes  dark  and  is  called  actinolite  (Nos.  3474,  3475), 
from  the  fact  that  it  occurs  in  blades  or  rays  (&KTLVOS,  "ray"). 

Tremolite  is  found  in  granular  dolomite  and  actinolite  in  schists 
in  the  Alps  and  Appalachians  (Nos.  582,  3435,  3444,  and  3446)  and 
other  mountainous  regions. 

Actinolite  is  strongly  pleochroic.  Light  passing  through  parallel 
to  a  is  greenish  yellow,  parallel  to  b  yellowish  green,  and  parallel  to 
c  green. 

SUMMARY 

Tremolite. — CaMg3(Si03)4;  CaO=i3-45  per  cent,  MgO  =  28.83  per 
cent,  Si02  =  57.72  per  cent.  Monoclinic;  a:b:c=o. 551:1:0. 294.  fi  = 
io6°2/.  (no),  (100),  (oio).  Twinning  plane  100.  Cleavage  (no)  per- 
fect; (100),  (oio)  imperfect.  Brittle;  fracture  uneven. 

Hardness  =  5 . 5 ;  gravity =3.1.  Pale  green;  vitreous;  translucent. 
Mean  refraction  (/?)  =  1.62;  maximum  (y)  =  i.63.  Double  refraction 
negative,  strong;  y— a  =  0.028.  Axial  plane  (oio);  acute  bisectrix  almost 
parallel  to  (ooi).  Axial  angle  (2N)  =  870  22';  p<v.  Extinction  angle 
(between  7  and  c)  =  i  5°. 

Fusible;  insoluble. 

Crystalline  dolomites  and  schists  in  many  mountain  regions. 

Hornblende 

Hornblende  is  the  common  black  amphibole  corresponding  to 
augite,  the  common  black  pyroxene.  It  may  be  distinguished  from 


154 


GUIDE  TO  MINERAL  COLLECTIONS 


augite  since  the  crystals  and  also  their  transverse  sections  are  usually 
six-sided  rather  than  eight-sided  (Figs.  196-99)  and  the  cleavage 
lines  parallel  to  prism  planes  make  an  angle  of  56°.  In  hardness, 
weight,  etc.,  the  two  minerals  are  similar. 

The  chemical  composition  of  hornblende  is  not  as  well  understood 
as  that  of  augite,  but  it  may  probably  be  best  represented  as  a 


Con) 


X<or) 

FIG.  196. — Hornblende 


—(010) 


FIG.  197. — Hornblende 


I 

1 

-!- 

..010 

I 

i 

j- 

,.O?o 

%/ 

S1/ 

FIG.  198.—  Horneblende  section  per- 
pendicular  to  prism. 


tot 

FIG.    199—  Hornblende   twinned  on 
(100). 


mixture  of  the  actinolite  molecule  Ca(Mg,Fe)3(Si03)4  and  a  molecule 
containing  aluminum  in  addition  to  the  calcium  and  magnesium, 
thus  CaMg2Al2(SiO4)3. 

Hornblende  is  found  in  lava,  as  at  Vesuvius,  and  in  basalt, 
trachyte,  gneiss,  and  schists  in  most  mountain  regions  (Nos.  3441, 

3442,  3443)- 

Excellent  crystals  weathering  out  of  volcanic  rocks  show  abundant 
twins  parallel  to  the  orthopinacoid  (100)  (Fig.  199). 


SILICATES 


155 


Hornblende. — 


SUMMARY 
Ca(MgFe)3(Si03)4 


CaMg2Al2(Si04)3 


Crystallography  the  same  as  that 


of  tremolite,  but  end  planes  are  common;    (ooi),   (on),   (101),   (130). 
Cleavage  parallel  (no)  with  angle  of  56°  perfect.    Brittle  to  tough. 

Hardness  =  5 . 5 ;  gravity =3. 2.  Dark  green  to  black;  vitreous; 
translucent  to  opaque.  Color  and  optical  properties  vary  with  the  amount 
of  iron  present.  Mean  refraction  (ft)  =  1.64.  to  1.72.  Double  refraction 
positive,  strong;  y—a=o. 019  to  0.072.  Axial  plane  (oio).  Axial  angle 


--" r— 


FIG.  200. — Anthophyl- 
lite;  parallel  extinction. 


FIG.    201. — Tremolite; 
extinction  angle  15°. 


\ 


FIG.  202. — Hornblende; 
extinction  angle  25°. 


59°.  Extinction  angle  (between  y  and  c)  =  i$°.  Strong  interfer- 
ence; strong  pleochroism,  c  greenish  blue,  b  emerald  green,  a  greenish 
yellow. 

Fuses  readily  and  may  become  magnetic;  insoluble. 

Mountain  ranges,  in  volcanic  and  metamorphic  rocks. 

Asbestos 

Asbestos  is  a  kind  of  amphibole  with  fibers  (Nos.  479,  480)  which 
are  of  sufficient  length  and  flexibility  to  permit  of  its  being  woven 
into  cloth.  In  northern  Italy  (Lombardy)  is  found  a  white  asbestos 
whose  silky  fibers  are  often  three  feet  long.  Usually  the  fibers  are 
but  an  inch  or  less  in  length.  When  too  short  for  weaving,  they  are 
used  for  insulation,  fireproof  packing,  etc.,  since  the  mineral  is  a  poor 


156  GUIDE  TO  MINERAL  COLLECTIONS 

conductor  of  heat  and  is  infusible.  The  greater  part  of  the  asbestos 
used  commercially  is  a  fibrous  variety  of  serpentine,  a  mineral  to  be 
described  later. 

" Mountain  cork"  and  ''mountain  leather"  are  matted  sheets  or 
nodules  of  yellowish  asbestos. 

Georgia  produces  amphibole  asbestos.  Arizona,  California,  and 
Wyoming  yield  serpentine  asbestos.  But  our  chief  supply  is  the 
chrysotile  (fibrous  serpentine)  imported  from  Canada.  It  is  woven 
into  cloth  (No.  1876)  for  theater  curtains,  gloves,  firemen's  suits,  etc.; 
made  into  yarn,  rope,  paper,  and  boards;  and  used  for  covering  steam 
pipes,  lining  safes,  making  paints,  filters,  etc. 

In  Griqualand,  Africa,  is  found  a  fibrous,  silky,  blue  chatoyant 
amphibole  known  as  crocidolite  (Nos.  3476  and  3478).  Through 
oxidation  and  partial  replacement  by  silica,  this  becomes  converted 
into  a  hard,  compact,  golden-yellow  mineral  known  as  " cat's  eye" 
or  "'tiger  eye,"  and  much  used  for  ornaments. 

Nephrite 

Nephrite  (jade)  is  another  variety  of  amphibole.  It  is  compact, 
has  a  specific  gravity  of  3,  and  is  harder  than  other  amphiboles,  its 
hardness  being  6.5.  It  is  one  of  the  toughest  of  minerals,  and  has  a 
splintery  fracture.  The  white  variety  has  the  composition  of  tremo- 
lite,  and  the  green  variety  that  of  actinolite.  On  account  of  its 
toughness,  color,  and  translucency,  like  jadeite  it  has  been  much 
prized  for  centuries  throughout  the  East  as  a  material  from  which 
to  carve  ornaments  and  weapons.  The  ancients  thought  it  a  cure  for 
kidney  diseases  (w0p6$,  "  kidney";  jade  has  the  same  meaning).  It  is 
found  as  bowlders  in  China,  India,  New  Zealand,  Alaska,  Mexico, 
and  Germany. 

Beryl 

When  beryllium  aluminium  silicate  (BCjAUSkOjg)  occurs  in 
greenish  masses  or  in  coarse,  hexagonal,  prismatic  crystals,  it  is 
called  beryl.  Transparent,  beautiful  pale-green  crystals  are  called 
aquamarine.  The  dark-green  crystals  are  called  emerald,  and  are 
among  the  most  prized  of  gem  minerals.  Aquamarine  means  sea 
water;  emerald  and  beryl  are  ancient  names  of  unknown  significa- 
tion (Fig.  2030). 


SILICATES 


157 


Beryl  furnishes  the  best  example  of  holosymmetric  hexagonal 
symmetry  found  among  minerals.  Little,  bright,  pale-green  crystals 
with  many  faces  occur  in  Siberia  and  in  the  Urals  (Fig.  2036). 

Ekaterinburg,  Russia,  has  long  been  known  as  a  good  source  for 
aquamarines  and  emeralds.  They  are  found  in  a  coarse  granite 
associated  with  topaz,  black  tourmaline,  and  smoky  quartz  in  the 
neighboring  mountains. 

A  tourmaline  granite  on  the  island  of  Elba  and  an  albitic  granite 
in  the  Mourne  Mountains,  Ireland,  contain  richly  terminated  beryls 
which  vary  in  tint  from  colorless  to  green,  blue,  or  red. 


FIG.     203  a. — Photograph    of    beryl 
from  Brazil,  (oooi)  and  (1010). 


FIG.  2036. — Beryl 


The  best  emeralds  have  been  procured  from  Muso,  Colombia,  in 
a  black,  bituminous  limestone,  where  they  are  accompanied  by 
pyrite,  calcite,  black  dolomite,  and  quartz.  The  prism  form  is 
strongly  developed.  The  crystals  have  often  been  fractured  and 
recemented  by  calcite. 

Coarse  beryl  of  gigantic  dimensions  has  been  found  in  New  Hamp- 
shire and  Massachusetts.  Nos.  1667,  3232,  and  500  represent  the 
New  Hampshire  locality.  No.  3483  conies  from  Connecticut. 
Colorado  (No.  3482)  and  North  Carolina  have  furnished  quantities 
of  beryl  and  a  few  emeralds. 

Beryl  crystals  are  often  striated  vertically  and  are  usually  without 
termination.  They  cleave  imperfectly  parallel  to  the  base.  Although 
without  doubt  hexagonal,  they  often  show  weak  double  refraction 


158 


GUIDE  TO  MINERAL  COLLECTIONS 


because,  of  strain.    They  resemble  apatite  but  may  be  distinguished 
by  their  inferior  cleavage  and  superior  hardness. 

Chromium  doubtless  furnishes  the  color  to  emerald  and  aqua- 
marine. Flawless  crystals  are  extremely  rare. 

SUMMARY 

Beryl. — Be3Al2Si60i8 ;  BeO  =  14.11  per  cent,  Al2O3  =  i9.os  per  cent, 
SiO2  =  66.84  per  cent.  Hexagonal;  holosymmetric;  a:  c=  1:0.4989. 
(1010),  (1011),  (2021),  (1121),  (2131),  (oooi).  Cleavage  parallel  (oooi) 
imperfect.  Brittle;  fracture  conchoidal. 

Hardness  =  7.5;  gravity=2.y.  Bluish  green;  vitreous;  transparent. 
w  =  i .  584;  double  refraction  negative,  weak;  w— e  =  o.oo6. 

Fusible  with  difficulty  (5.5).    Insoluble. 

Urals,  Maine,  New  Hampshire,  North  Carolina,  South  Dakota, 
Colorado. 

GARNET  GROUP 

Each  of  the  six  varieties  of  garnet  which  compose  this  group 
crystallizes  in  remarkably  well-formed  dodecahedrons,  trapezo- 

hedrons,  or  combina- 
tions of  these  forms 
(Figs.  204-6).  All  have 
imperfect  cleavage,  con- 
choidal fracture,  high  re- 
fraction, and  greasy 
luster.  In  color  they  are 
usually  red,  brown,  or 
black,  though  some 
varieties  are  green  or 
yellow. 

They  are  silicate  of 
calcium,  magnesium, 
manganese,  iron,  alumin- 
ium, and  chromium  in 
isomorphous  mixtures. 
Because  they  are  mix- 
tures their  color,  weight, 


Fig.  204. — Garnet 


fusibility,  and  solubility  are  variable,  as  may  be  seen  in  the  following 
table: 


PLATE  XXVII 


a,  Garnets;  dodecahedron  from  Salida,  Colorado,  trapezohedron  from  North 
Carolina,  and  combination  from  Fort  Wrangel,  Alaska. 


b,  A  dodecahedron  nearly  four  inches  in 
diameter  from  Salida,  Colorado. 


SILICATES 


159 


Grossularite,  Ca3Al2(SiO4)3;  gravity,  3.5;  hardness,  7;  fusible  (3); 
yellowish  to  red  or  brown. 

Pyrope,  Mg3Al2(Si04)3;  gravity,  3.7;  hardness,  7;  fusible  (3.5); 
deep  red  to  black. 

Almandite,  Fe3Al2(SiO4)3;  gravity,  3.5-4.3;  hardness,  7;  fusible  (3); 
deep  red  to  black. 

Spessarite,  Mn3Al2(SiO4)3;  gravity,  3.8;  hardness,  7;  fusible  (3); 
purple  red  to  brown. 

Uvarovite,  Ca3Cr2(SiO4)3;  gravity,  3.4;  hardness,  7;  infusible  (6); 
green. 

Andradite,  Ca3Fe2(SiO4)3;  gravity,  3.8-4.1;  hardness,  7;  fusible  (3); 
yellow,  red,  black. 

The  ordinary  varieties  of  garnet  are  abundant  enough  to  be 
mined  for  use  as  an  abrasive  in  New  York,  New  Hampshire  (No.  616), 
North  Carolina,  and  Georgia.  The  only  garnets  found  in  Illinois 
are  those  occurring  in  gneiss  and  schists  transported  from  the  north 

by  glaciers.  Dentists  use  garnet 
disks  for  polishing,  as  do  also 
shoe  manufacturers,  woodwork- 
ers, etc.  At  Morelos,  Mexico, 


FIG.  205. — Garnet 


FIG.  206. — Garnet 


a  marble  containing  large  pink  garnets  is  polished  for  ornamental 
slabs. 

Pyrope  (TTUPCOTTOS,  "fiery  eyed")  (Nos.  3489  and  3177)  and  alman- 
dite  are  much  used  in  common  jewelry,  the  former  often  being  of  a 
fine,  transparent  red  color  resembling  ruby,  and  the  latter  of  a  pur- 
plish or  hyacinth-red  color.  Almandite  is  often  cut  en  cabochon^ 
i.e.,  with  flat  base  and  rounded  top. 


160  GUIDE  TO  MINERAL  COLLECTIONS 

Uvarovite  (named  after  a  Russian  minister),  found  in  small, 
brilliant  green  crystals  in  a  serpentine  rock  in  the  Urals  and  in  granu- 
lar limestones  in  Canada,  is  cut  into  gem  stones  and  sold  as  "olivine," 
though  the  latter  mineral  is  no  harder  nor  superior  in  any  respect  to 
uvarovite. 

Under  the  microscope  garnet  crystals  show  square  or  hexagonal 
outlines  and  an  absence  of  cleavage.  They  are  isotropic  and  so 
strongly  refracting  (w=from  i  .7  to  i  .8)  as  to  present  a  bold  relief 
and  shagreenous  surface. 

Garnet  occurs  most  commonly  as  crystals,  from  the  size  of  a  pea 
to  that  of  a  boy's  marble,  in  crystalline  schists,  gneisses,  and  granulite, 
and  as  grains  in  phonolite  and  leucitophyre.  Sometimes  large  masses 
associated  with  hornblende  and  magnetite  constitute  a  garnet  rock. 
Garnet,  green  augite,  and  hornblende  form  eclogite,  which  is  by  some 
regarded  as  the  parent  rock  of  diamonds. 

Grossularite  (Nos.  3486,  3488,  3490),  the  lime  aluminium  garnet, 
is  typically  found  in  metamorphic  rocks,  such  as  marbles;  pyrope, 
the  magnesium  aluminium  garnet,  in  basic  rocks  containing  mag- 
nesium; almandite,  the  iron  aluminium  garnet,  and  spessartite,  the 
manganese  aluminium  garnet,  in  granitic  and  gneissic  rocks;  while 
andradite,  the  lime  iron  garnet,  is  of  widespread  occurrence. 

The  Urals,  Alps,  Pyrenees,  Appalachians,  and  Cordilleras  have 
all  furnished  multitudes  of  various  kinds  of  garnets. 

SUMMARY 

Garnet  —  (Ca,Mg,Fe,Mn)3(Al,Fe,Cr,)2(SiO4)3.  Regular;  no,  211. 
Cleavage  (no)  imperfect;  brittle;  fracture  uneven. 

Hardness  =  7  to  7.5;  gravity =3. 8.  Honey-yellow  to  black;  luster 
vitreous;  transparent;  (0  =  1.7-1.8. 

All  except  uvarovite  soluble  with  difficulty;  andradite  most  readily. 
Iron  garnets  fuse  to  magnetic  globules. 

Mountain  regions  generally. 

Zircon 

Zircon,  a  brown  zirconium  silicate,  nearly  always  occurs  in  crys- 
tals, since  it  is  one  of  the  first  minerals  to  solidify  out  of  the  molten 
magma  which  forms  augite  syenite,  elaeolite  syenite,  and  other 
igneous  rocks.  In  crystalline  schists  and  gneiss  the  crystals  are 
usually  microscopic  in  size,  but  may  be  readily  identified  by  their 


SILICATES 


161 


square  outlines,  brown  color,  and  by  their  high  refraction  (1.930) 
and  double  refraction  (o  .062),  which  give  them  a  bold  relief  and  in  an 
ordinary  rock  section  interference  colors  of  the  third  order.  Because 
of  its  hardness  and  insolubility  zircon  resists  decomposition,  and  is 
found  with  gold,  platinum,  cassiterite,  and  magnetite  in  the  heavy 
sands  which  result  from  the  destruction  of  granites  and  gneisses. 

Figures  207  and  208  represent  the  common  forms  of  the  simple 
crystal.  By  enlargement  of  the  pyramid  (311)  acute  termination 
results.  With  zircon,  as  with  cassiterite  and  quartz,  basal  planes  are 
rarely  developed. 

Clear  varieties  (No.  3494)  are  much  prized  as  gems  because 
of  their  hardness  (7.5),  high  refraction,  and  great  dispersion.. 


311 


FIG.  207. — Zircon 


FIG.  208. — Zircon 


In  refraction  and  dispersion  they  come  next  to  diamonds.  Ini 
color  they  vary  from  colorless  through  various  shades  of  orange, 
yellow,  red  ("jacynth"),  pale  green,  and  gray  ("jargoon").  When, 
dark  brown  they  become  opaque.  The  color  is  due  to  Fe2O3  and 
can  be  altered  by  heating  in  the  blowpipe  flame. 

When  finely  powdered,  zircon  is  slowly  decomposed  in  hot  sul- 
phuric acid. 

Ceylon,  the  Urals,  Alps,  Norway,  North  Carolina,  Arkansas,  and 
Colorado  have  all  furnished  fine  specimens  of  zircon. 

SUMMARY 

Zircon.— ZrSiO4 ;  Zr02  =  67 . 2  per  cent ;  SiO2 = 3 2 . 8  per  cent.  Tetrag- 
onal; holosymmetric.  a:c=  1:0.64.  (in),  (311),  (100),  (no).  Cleav- 
age parallel  (in),  (no),  imperfect.  Brittle;  fracture  conchoidal. 


162 


GUIDE  TO  MINERAL  COLLECTIONS 


Hardness  =  7.5;  gravity =4.7.    Brown ;  luster  adamantine ;  subtrans- 
lucent;  w  =  i  .93.    Double  refraction  positive,  strong;  e— co=o.o62. 
Infusible;  insoluble. 
Ceylon,  Urals,  Norway,  North  Carolina,  Colorado. 

Topaz 

The  name  topaz  is  given  to  a  mineral  which  is  hard,  colorless, 
transparent,  prismatic,  often  vertically  striated,  usually  terminated 
at  one  end  by  several  pyramid  planes  and  a  basal  plane,  easily  cleav- 
able  parallel  to  the  base,  and  in  chemical  composition  is  a  silicate  of 
aluminium  and  fluorine  Al2(FOH)2SiO4. 


FIG.  209. — Topaz 


FIG.     210. — Topaz,    showing    optic 
axes  (o)  and  axial  plane. 


Many  crystals  are  delicately  or  deeply  colored.  Pale-blue  crys- 
tals are  found  with  orthoclase,  smoky  quartz,  and  beryl  in  granite 
at  Nerchinsk,  Siberia  (No.  1890);  and  dark-blue  crystals  at  Mursinsk 
in  the  Urals  in  a  similar  rock  accompanied  by  lepidolite.  Deep 
brown  crystals  are  found  on  the  Urulga  River  in  the  Urals,  and  in 
Minas  Geraes,  Brazil  (No.  3493).  The  brown  crystals  when  heated 
often  become  pink.  Some  regions  furnish  golden-yellow  crystals, 
but  the  great  majority  of  occurrences  are  white  or  colorless.  Many 
limpid,  richly  planed  crystals  are  found  in  Utah  and  Colorado. 

Like  cassiterite,  topaz  was  formed  under  the  influence  of  heat  and 
in  the  presence  of  vapors  containing  fluorine. 

Attractive  color,  together  with  high  refraction  and  great  hard- 
ness, places  topaz  among  the  gems. 


SILICATES  163 

SUMMARY 

Topaz.— Al2(FOH)2SiO4;  Al2O3=55-44  per  cent,  F=2o.6s  per  cent, 
SiO2  =  32.6i  per  cent.  Orthorhombic;  a:b:c  =  o. 528: 1:0.477.  X001), 
(in),  (no),  (120),  (221),  (223),  (201),  (021),  (041),  (140).  Cleavage 
parallel  (ooi)  perfect.  Brittle;  fracture  sub-conchoidal. 

Hardness  =  8;  gravity =3. 5.  Pale  yellow;  vitreous;  transparent. 
/3=i.6i8;  7=1.623.  Double  refraction  positive,  weak;  y—  a=o.on. 
Axial  plane  (oio) .  Acute  bisectrix  normal  to  (ooi) ;  2  E  =  1 14°.  Dispersion 
strong;  p>v. 

Infusible;  difficultly  soluble. 

Urals,  Brazil,  Japan,  Utah,  Colorado,  California,  Missouri. 

Cyanite 

This  mineral  (No.  3496),  which  easily  attracts  attention  because 
of  its  blue  color  (/cuapos,  "blue"),  occurs  in  long,  flat,  bladed  crystals 
that  show  a  remarkable  difference  in  hardness  in  different  directions. 
Across  the  blades,  that  is,  parallel  to  the  edge  made  by  the  macro- 
pinacoid  (100)  and  base  (ooi),  the  hardness  is  7,  while  along  the 
crystal,  that  is,  parallel  to  the  edge  formed  by  the  macropinacoid 
(100)  and  brachypinacoid  (oio),  the  hardness  is  only  4.5.  When 
Haiiy  discovered  this  property,  he  named  the  mineral  disthene 
(dis  and  Oevos,  " double  strength").  When  cyanite  is  heated  at 
1350°  C.  without  changing  its  chemical  composition  (Al2SiOs)  it  is 
transformed  into  a  fibrous  mineral  of  uniform  hardness  (6.5),  lighter 
specific  gravity  (3.2;  cyanite  is  3.6),  and  straight  extinction.  The 
mineral  is  called  sillimanite,  and  is  characteristic  of  some  gneisses 
and  schists.  Compact  sillimanite  (sometimes  wrongly  called  jade) 
was  used  in  prehistoric  times  in  the  manufacture  of  ornaments  and 
implements. 

SUMMARY 

Cyanite. — Al2SiOs;  A1203  =  63  per  cent,  Si02  =  37  per  cent.  Triclinic; 
a:b:c=o.Sgg:  1:0.697.  (ooi),  (100),  (oio),  (no).  Cleavage  parallel 
(100)  perfect;  (oio)  imperfect.  Brittle;  fracture  fibrous. 

Hardness  =7  across  the  crystal,  4.5  parallel  to  the  edge  (100);  (oio); 
gravity =3. 6.  Blue  to  white;  vitreous;  transparent.  (3  =  i.j2.  Double 
refraction  negative;  y— a  =  o.oi6.  Axial  plane  inclined  30°  to  edge  (100); 
(oio).  Acute  bisectrix  normal  to  100: 2  H  =  ioo°. 

Infusible;  insoluble. 

Alps,  northern  England,  Appalachians,  Cordilleras. 


164 


GUIDE  TO  MINERAL  COLLECTIONS 


Tourmaline 

This  mineral  is  worthy  of  notice  for  three  reasons:  first,  because 
it  is  abundant  in  igneous  and  metamorphic  rocks;  second,  because  it 
is  used  in  making  optical  instruments  such  as  " tourmaline  tongs" 
(see  below,  p.  166);  and  third,  because  the  beautiful  red,  pink,  and 
green  varieties  are  used  as  gems  (Plate  XXVIII).  Tourmaline  is 
literally  found  "from  Maine  to  California."  Paris,  Maine  (Nos.  444, 
454,  4062),  has  long  been  reputed  for  its  magnificent  red  and  green 
crystals,  and  more  recently  San  Diego  County,  California  (Nos.  3511, 
3788,  3789,  3790),  has  furnished  the  museums  of  the  world  with 
handsome  groups  of  red  tourmaline  (rubellite)  in  a  lavendar  mica, 
lepidolite.  The  tourmalines  of  Illinois  are  all  emigrants  from  northern 


FIG.  211. — Tourmaline 


FIG.  212. — Tourmaline 


regions.  Black  is  the  prevailing  color,  and  they  are  usually  imbedded 
in  gneisses  and  granites.  Among  the  most  famous  foreign  localities 
may  be  mentioned  the  region  near  Ekaterinburg  in  the  Urals,  where 
a  coarse  granite  contains  smoky  quartz,  albite,  green  and  pink  mica, 
and  red  and  fine  black  tourmaline.  At  Campologna,  Switzerland, 
calcite,  corundum,  diaspore,  mica,  and  green  tourmaline  are  found 
in  a  granular  dolomite.  The  granite  of  the  island  of  Elba  consists 
of  quartz,  orthoclase,  albite,  mica,  pink  beryl,  red  garnet,  and  red 
and  black  tourmaline.  The  best  gem  tourmalines  are  obtained  in 
Ceylon. 

Tourmaline  crystals  (Nos.  357  and  3505)  (Figs.  211  and  212)  are 
usually  prismatic,  often  elongated,  sometimes  terminated  at  one  end, 


PLATE  XXVIII 


a,  Tourmaline  doubly 
terminated;  variously  colored 
crystal  from  Mesa  Grande, 
California. 


b,  Black,  well-crystallized 
specimen  from  Haddam,  Con- 
necticut. 


SILICATES  165 

rarely  at  both  ends.  Occasionally  they  are  flat  crystals.  Prisms 
are  strongly  striated  vertically.  This  striation,  the  triangular  cross- 
sections,  and  absence  of  cleavage  serve  to  distinguish  this  mineral 
from  black  pyroxenes  and  amphiboles. 

The  chemical  constitution  of  tourmaline  is  complex  and  is  still 
the  subject  of  much  discussion.  Generally  speaking,  it  is  a  borosili- 
cate  of  aluminum,  iron,  or  chromium,  of  magnesium,  and  of  the 
alkalies  sodium,  potassium,  and  lithium.  The  following  varieties 
may  be  distinguished: 

Black,  iron  tourmaline  (Fe4Na2B6AlI4H8SiI2O63) ;  gravity =3. 2. 

Red,  green,  colorless;  alkali  tourmaline  (NaLiK^BeAl^HgSinOej) ; 
gravity  =  3. 

Brown;  colorless;  magnesium  tourmaline  (MgI2B6AlIOH8SiI2063) ; 
gravity  =  3. 

Green;  chromium  tourmaline  (chromium  replacing  a  portion  of 
the  aluminium) ;  gravity  =  3.1. 

Transparent  crystals  (No.  3788)  are  often  differently  colored  at 
the  different  ends,  and  some  are  banded  with  two  or  three  different 
shades  of  color,  as  may  be  observed  in  a  section  parallel  to  the  base. 

Early  in  the  eighteenth  century 
it  was  discovered  that  red  tourma- 
line crystals  brought  from  Ceylon 
when  heated  became  positively 
electrified  at  one  end  and  nega- 
tively at  the  other.  When  any 
tourmaline  crystals  after  heating 
are  beginning  to  cool,  if  they  are 
dusted  with  finely  powdered  red 
lead  (-f)  and  sulphur  (— ),  one 
end — the  negative,  the  "analogous 

end" — attracts  the  red  lead,  while          FIG.  213— Tourmaline,  analogous 
the  other — the  positive  or  "antilo-       end. 
gous  end" — attracts  the  sulphur. 

The  negative  end  (No.  3791)  usually  shows  a  basal  plane  and  the 
rhombohedron  (R)  over  the  trigonal  prism  (1010)  (Fig.  213).  The 
positive  end  is  usually  acute  owing  to  the  development  of  pyramids. 
All  tourmalines  absorb  the  ordinary  ray  much  more  completely  than 
they  do  the  extraordinary,  consequently  black  varieties  look  green  or 


i66 


GUIDE  TO  MINERAL  COLLECTIONS 


blue  with  the  ordinary  ray  (o)  and  brown  or  red  with  the  extraordi- 
nary (e).  Brown  crystals  cut  parallel  to  the  optic  axis  transmit 
only  the  extraordinary  ray,  and  can  be  used  as  polarizer  and  analyzer. 
Two  such  sections  held  in  wire  rings  constitute  "  tourmaline  tongs." 

SUMMARY 

r^rwa/^e.— (FeCrNaKLi)4MgI2B6AlI6H8SiI2O63.  Hexagonal;  sym- 
metry ditrigonal  polar;  a:c=  1:0.4477.  (oooi),  (1011),  (0221),  (1010), 
(1120),  (3251).  Cleavage  imperfect  parallel  (1011).  Brittle;  fracture 
subconchoidal. 

Hardness  =  7;  gravity =3.1.  Black,  brown,  red,  green,  colorless; 
vitreous;  translucent;  00  =  1.64.  Double  refraction  strong,  negative; 
w— €=0.017.  Pleochroic;  pyro-electric. 

Fusible;  insoluble. 

Maine  to  California,  Urals,  Alps. 

ZEOLITE  GROUP 

The  zeolites  (£eco,  "I  boil")  are  white,  pearly,  light  (gravity,  2), 
soluble  minerals,  which  boil  before  the  blowpipe  because  the  two  to 


FIG.  214. — Four-twinned  crystals  of 
stilbite. 


FIG.  215.— Stilbite  sheaf 


six  molecules  of  water  of  crystallization  contained  in  them  are  loosely 
held.  The  different  members  of  the  group  are  so-called  "  secondary 
minerals"  since  they  result  from  the  decomposition  of  other  minerals, 
chiefly  feldspar,  leucite,  etc.,  in  disintegrating  igneous  rocks.  From 
seventeen  representatives  three  may  be  chosen  to  indicate  the  nature 
of  the  group. 

Stilbite 

The  most  attractive  characteristic  about  this  mineral  is  its  pearly 
sheaflike  crystals  (Nos.  3255  and  3514),  which  result  from  twinning 


SILICATES 


167 


of  monoclinic  crystals  parallel  to  the  base  and  orthodome  in  such  a 
manner  as  to  produce  interpenetrating  twins.  The  crystals  are 
flattened  parallel  to  the  clinopinacoid,  which  is  also  a  plane  of  easy 
cleavage.  The  basal  cleavage  is  imperfect.  The  basaltic  rocks 
found  in  many  places  in  New  Jersey,  Michigan,  the  Cordilleras, 
Scotland,  etc.,  contain  in  their  cavities  fine  groups  of  stilbite  crystals. 

SUMMARY 

Stilbite.— CaAl2Si6Oi6+6H2O;  CaO  =  8.94  per  cent,  A1203  =  16.31  per 
cent,  Si02  =  S7.si  per  cent,  H20  =  i7.24  per  cent.  Some  Na2  usually 
replaces  a  portion  of  the  Ca.  Monoclinic;  0:6: 6  =  0.7623:1: 1:1940. 
/?  =  5o°5o'  (ooi),  (oio),  (no).  Twinned  parallel  (ooi)  and  (101).  Cleav- 
age parallel  (ooi).  Brittle;  fracture  uneven. 

Hardness  =  3.5;  gravity  =2.2.  White ;  vitreous ;  transparent ;  ft  = 
1.498.  Double  refraction,  strong,  negative;  y— a  =  0.006.  Axial  plane 
(oio)  acute  bisectrix  inclined  85°  to  normal  of  (ooi)  and  34°  to  the  normal 
of  (100).  2  £  =  51. 5. 

Fusible  (2.5).    Decomposed  by  hydrochloric  acid. 

In  disintegrating  igneous  rocks  in  the  Cordilleras,  Appalachians 
Scotland,  etc. 

Analcite 

The  second  representative  of  the  zeolites  to  claim  our  attention 
is  analcite  (No.  3576),  one  of  the  best  illustrations  of  the  trapezohedral 
crystals  among  minerals  (Fig. 
216).  More  rarely  analcite 
occurs  in  cubes  with  corners 
truncated  by  the  trapezohe- 
drons.  Small  crystals  are  often 
beautiful  and  glossy.  The  larger 
ones  are  usually  opaque  and 
white  or  pink. 

SUMMARY 

Analcite.—  Na2Al2Si4OI2+2H2O; 
Na20  =14.1  per  cent,  A12O3  =  23 . 2 
per  cent,  Si02=54.5  per  cent, 
H2O  =  8.2  per  cent.  Regular; 
(211),  (100).  Brittle;  fracture 
uneven. 

Hardness  =  5.5;     gravity  =2.2. 
#=1.487. 

Fusible  (2.5).     Gelatinizes  in  hydrochloric  acid. 

Same  regions  as  other  zeolites. 


FIG.  216.— Leucite 
Colorless;     vitreous;     transparent. 


i68 


GUIDE  TO  MINERAL  COLLECTIONS 


FIG.  217. — Natrolite 


Natrolite 

Natrolite  (No.  3517)  is  closely  related  to  analcite  in  chemical 
composition  inasmuch  as  it  contains  one  less  molecule  of  SiO2,  but 
differs  markedly  in  form  since  it  crystallizes  in  the  orthorhombic 
system  and  occurs  in  long  prisms  that  end  in  very  flat  pyramids. 

It  is  the  commonest  of  fibrous  zeolites,  usually  constituting  masses 
in  cavities.  Beautiful  tufts  of  acicular  crystals 
are  found  in  the  cavities  of  basalt. 

So  fusible  is  it  that  it  melts  in  a  candle  flame, 
imparting  the  yellow  color  characteristic  of  burn- 
ing sodium. 

SUMMARY 
110 

Natrolite—  Na2Al2Si3OIO  •  2H2O  ;    Na2O  =  16 . 32 

per  cent,  A12O3=26.86  per  cent,  SiO2=47.36  per 
cent,  H2O  =  g\46  per  cent.  Orthorhombic;  a:b:c  = 
0.978:1:0.354.  (no),  (in).  Cleavage  parallel  (no) 
perfect.  Brittle;  fracture  uneven. 

Hardness  =  5 . 5 ;      gravity  =2. 2.     Colorless;     vitreous;      transparent. 
/8=i.479.     Double  refraction  positive,  strong;  y—a  =  o.oi2.     Axial  plane 
(oio).    Acute  bisectrix  normal  to  (ooi).     2  £=99°;  p<v. 
Fuses  readily  (2).     Gelatinizes  in  hydrochloric  acid. 
In  basalts  in  the  Cordilleras,  Michigan,  New  Jersey,  etc. 

MICA  GROUP 

While  zeolites  are  comparatively  rare,  the  members  of  the  mica 
group  are  among  the  most  abundant,  well-known,  and  useful  of 
minerals.  The  thin,  flexible,  elastic  leaves  into  which  mica  may  be 
separated  distinguish  it  so  clearly  that  once  seen  it  is  not  forgotten. 

From  the  seven  members  of  the  group  the  three  most  striking 
and  abundant  are  white  mica,  muscovite,  "isinglass";  black  mica, 
biotite;  and  lilac  mica,  lepidolite. 

Together  with  quartz  and  feldspar,  micas  are  common  in  the 
granites,  gneisses,  and  schists.  The  minerals  of  this  group  are 
always  crystallized  and  never  massive.  The  crystals  vary  from 
minute  flakes  to  immense  sheets  which  measure  sometimes  several 
feet  across.  In  some  localities  in  Russia,  India,  Canada,  and  the 
United  States,  deposits  are  being  mined  which  furnish  sheets  of  large 
size. 


SILICATES 


169 


The  crystals  are  flat  monoclinic  prisms  having  six  sides  and  often 
so  regularly  shaped  as  to  appear  to  belong  to  the  hexagonal  or  ortho- 
rhombic  system  (Fig.  218).  Accurate  measurements  and  optical 
investigations,  however,  reveal  their  monoclinic  symmetry.  The 
angles  between  the  prism  planes  are  always  about  120°. 

The  micas  are  all  silicates  of  aluminium  and  of  either  potassium, 
sodium,  and  lithium — the  alkali  micas — or  of  iron  and  magnesium — 
the  ferro-magnesium  mica;  and  contain  also  fluorine  and  hydrogen. 


in 

FIG.  218. — Muscovite 


FIG.  219. — Muscovite:  pressure  fig- 
ure dotted;  percussion  figure  solid; 
optic  axes. 


Inclusions  of  other  minerals,  such  as  hematite,  tourmaline,  garnet, 
etc.,  are  common  and  are  arranged  as  flat  scales  along  definite  lines 
marked  out  by  the  so-called  glide  planes.  When  minute  they  often 
produce  the  attractive  property  known  as  asterism. 

Muscovite 

White  mica  is  called  muscovite,  from  Moscow,  where  it  and  a 
substance  resembling  it  in  appearance — gelatin,  derived  from  the 
sturgeon  so  abundant  in  Russian  rivers — were  long  used  for  window 
panes  and  other  purposes.  It  is  the  potassium  mica,  H2KAl3(SiO4)3. 
Its  crystals  often  attain  large  size.  They  are  six-sided,  rough-faced, 
and  taper  because  of  the  dome  planes  (Nos.  3519,  3520,  378,  1281). 
Besides  the  excellent  cleavage  parallel  to  the  base  (ooi),  no  other 
cracks  are  apt  to  be  found  in  thin  sections.  But  by  pressure  with  a 
blunt-pointed  instrument  three  sets  of  cracks  ,(the  dotted  line  in 
Fig.  219),  the  so-called  pressure  figures,  are  formed.  The  cracks 


170  GUIDE  TO  MINERAL  COLLECTIONS 

correspond  to  the  glide  planes  which  are  parallel  to  the  clinodome  (205) 
and  the  pyramid  (135).  When  developed  in  nature  these  cracks 
divide  the  crystal  into  trigonal  pieces. 

The  percussion  figure  produced  by  striking  a  cleavage  plate  with 
a  sharp-pointed  instrument  consists  of  a  six-rayed  star  in  which  the 
rays  intersect  at  angles  of  60°  (the  solid  lines  in  Fig.  219).  The 
most  prominent  crack  is  parallel  to  the  brachypinacoid  (oio),  which 
is  the  plane  of  symmetry. 

In  muscovite  the  axial  plane  is  perpendicular  to  the  principal 
crack  of  the  percussion  figure  and  hence  parallel  to  the  macropinacoid 
(100).  Hence  muscovite  is  called  " macrodiagonal  mica"  or  mica  of 
the  first  class. 

Muscovite  is  formed  both  in  fused  magmas  and  in  aqueous  solu- 
tions. 

Its  uses  are  many:  by  the  Russians  for  windows  in  war  vessels, 
by  the  French  for  decoration  and  ornamentation,  by  the  Anglo- 
Saxons  for  various  commercial  purposes. .  It  furnishes  doors  for 
stoves  and  furnaces.  It  is  used  for  electrical  purposes.  It  serves  as 
a  non-conductor  of  heat  and  electricity.  It  is  an  absorbent  of  nitro- 
glycerine; it  is  a  lubricant.  In  short,  it  is  a  mineral  much  used 
by  man. 

SUMMARY 

Muscovite.— H2KAl3(Si04)3;  K20=n.8  per  cent,  A12O3=38.5  per 
cent;  Si02=45.2  per  cent,  H20  =  4.5  Per  cent-  Monoclinic;  a:b:c  = 
o-5777:i:3-3i2.  £=89°  54'.  (ooi),  (in),  (221),  (no),  (oio).  Twins 
parallel  (no)  are  combined  on  the  base  (ooi).  Cleavage  parallel  (ooi). 
Elastic;  fracture  uneven;  chief  percussion  figure  parallel  to  (oio). 

Hardness  =  2. 5  per  cent;  gravity  =2. 86.  Axial  plane  perpendicular 
to  (oio);  ft  =1.6.  Double  refraction  negative,  strong;  y— a =0.039; 
p>v.  Pleochroism  feeble ;  transparent,  white;  vitreous. 

Fusible  with  difficulty;  insoluble. 

In  granites,  gneisses,  mica  schists,  in  all  mountain  ranges.  New 
Hampshire,  South  Carolina,  South  Dakota,  Colorado,  New  Mexico,  and 
California. 

Biotite 

Black  mica,  named  biotite  after  Biot,  the  celebrated  French 
mineralogist,  is  the  magnesian  mica  (H,K)2(Mg,Fe)2Al2(SiO4)s 
(Nos.  3535,  3536,  1240,  1768,  453). 


SILICATES 


171 


In  this  mica  the  axial  plane  is  usually  parallel  to  the  chief  per- 
cussion figure,  which,  as  noted  above,  is  parallel  to  the  brachypinacoid 
(oio).  Such  biotite  is  said  to  be  a  brachy diagonal  mica,  or  mica 
of  the  second  class. 

Whether  muscovite  or  biotite  is  the  more  abundant  mica  is 
difficult  to  say,  since  both  abound  in  nearly  all  kinds  of  igneous 
rocks.  Biotite  decomposes  more  readily  than  muscovite  and  forms 
such  minerals  as  chlorite,  epidote,  quartz,  and  iron  oxide.  Its 


FIG.  220. — Biotite;  axial  plane  parallel 
to  (oio). 


FIG.  221. — Basal  section  of 
biotite,  showing  position  of  axial 
plane  and  percussion  figure. 


characteristic  color  is  black,  but  while  undergoing  decomposition  it 
assumes  red  and  green  shades.  It  is  strongly  pleochroic  and  appar- 
ently uniaxial.  Fine  crystals  are  found  at  Vesuvius. 

SUMMARY 

Biotite—  (H,K)a(Mg,Fe)aAi2(SiO4)3;  K2O=7.64  per  cent,  MgO  =  2i  .89 
per  cent,  H2O  =  4.02  per  cent,  F  =  o.8g  per  cent,  Fe2O3=7.86  per  cent, 
A12O3=  16.95  Per  cent,  SiO2=39-3o  per  cent.  A  little  FeO,  MnO,  CaO, 
and  Na2O  are  usually  present.  Monoclinic;  a:b:c=o. 577:1:3. 2 74. 
/3=9o°.  (no),  (in),  (ooi),  (oio),  (221).  Twinning  plane  parallel  to 
(no),  combination  face  (ooi).  Cleavage  parallel  to  (ooi)  perfect;  laminae 
elastic;  fracture  uneven. 

Hardness  =  2.5;  gravity  =  2 . 86.  Black,  pleochroic ;  a  green,  /?  and  y 
dark  brown.  Translucent;  luster  vitreous;  streak  colorless.  Plane  of 
optic  axes  parallel  to  (oio).  Acute  bisectrix  inclined  30'  to  the  perpen- 
dicular of  (ooi).  J3=i.6.  Double  refraction  negative,  strong;  y— a= 
0.04;  p<v;  2E=i2°48'. 

Fusible  with  difficulty;  soluble  in  sulphuric  acid. 

Maine,  North  Carolina,  Colorado. 


172  GUIDE  TO  MINERAL  COLLECTIONS 

Lepidolite 

This  beautiful  violet  mica  (No.  553)  occurs  in  small  flakes  only 
(\€7Tts,  "scale").  It  is  usually  accompanied  with  other  lithium 
minerals  such  as  tourmaline.  The  violet  color  is  probably  due  to 
manganese.  San  Diego,  California,  has  within  the  last  few  years 
supplied  most  of  the  museums  of  the  country  with  fine  specimens  of 
lepidolite. 

SUMMARY 

Lepidolite. — Li2K2F2Al3H2Si6O2o;  Li2O=i  to  6  per  cent,  K2O  =  4  to 
10  per  cent,  F=2  to  8  per  cent,  A12O3  =  26  to  33  per  cent,  Si02=49  to 
52  per  cent.  Monoclinic;  crystallographic  and  optical  properties  similar 
to  those  of  the  other  micas,  but  the  axial  plane  is  sometimes  parallel  and 
sometimes  perpendicular  to  the  plane  of  symmetry. 

Hardness  =2.5;  gravity =2.8.    Lilac  or  rose-colored. 

Partly  soluble  in  hydrochloric  acid. 

Maine,  Massachusetts,  Connecticut,  California. 

SERPENTINE  AND  TALC  GROUP 

These  two  magnesian  silicates  are  common  decomposition  prod- 
ucts of  other  ferro-magnesian  silicates.  They  are  basic  salts  and  not 
hydrated,  inasmuch  as  they  part  with  their  water  at  high  tempera- 
tures only.  Like  most  secondary  minerals  they  are  soft.  Crystalli- 
zation is  inconspicuous.  They  occur  most  commonly  in  compact 
masses  in  veins  or  beds. 

Serpentine  * 

Serpentine  is  a  green,  red,  or  yellow  mineral  often  more  or  less 
fibrous  in  structure,  as  may  be  seen  under  the  microscope  in  those 
masses  which  fill  veins.  At  times  the  fibers  are  well  pronounced  and 
silky  in  luster,  and  the  mineral  is  then  called  chrysotile — the  most 
abundant  asbestos  (No.  3540).  The  fibers  are  longer,  more  tenacious 
and  silky  than  those  of  the  amphibole  asbestos.  The  most  produc- 
tive asbestos  mines  in  North  America,  those  in  Megantic  and  Beauce 
counties,  Quebec,  furnish  the  chrysotile  variety  of  asbestos.  Arizona, 
California,  and  Wyoming  are  furnishing  small  quantities. 

Some  serpentines  supply  ornamental  stones  of  great  beauty 
(Nos.  4336,  4337).  The  permanent  dark-green  color  is  rendered 
even  more  attractive  by  white  particles  of  magnesite  and  talc,  and 


SILICATES  173 

by  splashes  of  blood-red  iron  stains.     "  Verde  antique  "  is  a  brecciated 
serpentine. 

SUMMARY 

Serpentine. — H4Mg3Si2O9;  MgO=43-5  per  cent,  Si02=43.5  per  cent, 
H2O=i3  per  cent.  Massive;  fracture  splintery. 

Hardness=3;  gravity  =2. 6.  Green;  luster  greasy;  translucent; 
ft=  i . 57.  Double  refraction  negative,  weak;  y— a=o.oio. 

Fusible  with  difficulty  (6).    Soluble  in  hydrochloric  acid. 

Appalachians,  Cordilleras,  Alps,  etc. 

Talc 

Talc  is  a  foliated,  silvery,  soft,  greasy  mineral.  Though  the 
flakes  show  hexagonal  outline,  yet,  like  mica,  talc  is  monoclinic.  The 
angle  between  the  optic  axes  is  very  small.  In  many  regards  talc 
resembles  one  of  the  micas,  phlogopite,  but  is  softer  and  not  elastic 
(Nos.  353,  368).  Talc  usually  contains  from  i  to  4  per  cent  of  iron 
oxide. 

The  compact  varieties,  such  as  steatite  or  soapstone,  were  used  by 
the  Chinese  in  ancient  times  for  ornaments  and  images,  and  by 
savage  and  civilized  peoples  today.  A  clearer  conception  of  the  value 
of  the  mineral  industry  in  the  United  States  may  be  gained  by  the 
knowledge  that  while  talc  is  a  mineral  rarely  mentioned,  more  than 
a  million  dollars'  worth  of  it  are  produced  in  the  United  States 
annually  and  manufactured  into  such  articles  as  bath  and  laundry 
tubs,  sinks,  mantles,  hearthstones,  fire  brick,  griddles,  slate  pencils, 
gas  tips,  crayons,  French  chalk  for  tailors,  adulterant  for  sugars, 
lubricators  for  dressing  skins  and  leather,  toilet  powders,  dynamite, 
paper-making,  pigments  in  high-grade  paints,  etc.  New  York  is  the 
leading  state  in  the  production  of  talc  and  Virginia  in  soapstone. 

SUMMARY 

Talc. — H2Mg3(Si03)4;  MgO  =  3i.7  per  cent,  SiO2=63.5  per  cent, 
H20=4.8  per  cent.  Monoclinic.  Cleavage  parallel  (ooi)  perfect;  sectile, 
pliable. 

Hardness=i;  gravity  =2. 7.  Color  silver  white;  luster  pearly; 
translucent.  ^8=1.55.  Double  refraction  negative,  strong;  y— a =0.040. 
Acute  bisectrix  normal  to  the  cleavage.  2  £=19°. 

Almost  infusible.    Insoluble. 

The  Alps,  Appalachians,  Cordilleras,  etc. 


174  GUIDE  TO  MINERAL  COLLECTIONS 

Kaolinite 

Decomposition  of  orthoclase,  albite,  leucite,  beryl,  and  other 
minerals  often  gives  rise  to  a  secondary  mineral,  kaolinite,  which  is  a 
hydrated  aluminous  silica,  H4Al2Si2O9.  The  pure  form  is  kaolinite 
(from  the  Chinese  kaolvng,  "high  ridge").  As  various  impurities 
such  as  iron,  calcium,  and  magnesium  increase,  various  clays  result. 
In  structure  and  other  physical  characters  kaolinite  resembles  the 
hydrated  magnesian  silicate  serpentine.  It  is  white,  scaly,  flexible, 
inelastic,  soft  (hardness,  2),  light,  (gravity,  2.6),  unctuous,  and 
plastic. 

Some  clays  have  absorbent  properties  which  render  them  valuable 
as  fuller's  earth.  Others  fuse  at  such  temperatures  and  yield  a  product 
of  such  character  as  to  be  valuable  for  porcelain,  china,  tile,  brick,  etc. 
Others  are  plastic  because  of  the  elongated  particles  which  constitute 
them,  and  are  useful  in  clay-modeling. 

Various  varieties  of  clays  are  among  the  most  abundant  mineral 
constituents  of  the  regolith  covering  Illinois.  They  form  soil  for 
agriculture  and  plastic  material  for  the  manufacture  of  tile,  porcelain, 
brick,  etc.  Their  contribution  thus  to  the  wealth  of  the  state  is 
difficult  to  estimate.  The  value  of  clay  products  sold  annually  in  this 
state  amounts  to  more  than  fifteen  million  dollars,  but  this  takes 
no  account  of  the  return  through  soil  fertility.  Clay  soils  are  useful 
chiefly  in  furnishing  a  binder  for  more  porous  soil,  as  retaining  moisture, 
and  as  being  a  container  for  other  plant  food. 

SUMMARY 

Kaolinite.— H4Al2Si2O9;  A12O3  =  39-S  Per  cent>  Si02=46.5  per  cent, 
H20  =  i4  per  cent.  Water  is  driven  off  at  330°.  Monoclinic.  Scales 
flexible,  inelastic;  friable  to  compact;  unctuous,  plastic. 

Hardness=2.s;  gravity  =2. 6.  White,  blue,  yellow,  red,  green; 
luster  pearly  to  earthy;  translucent.  Biaxial,  negative. 

Infusible;  insoluble.    Blue  color  with  cobalt  solution. 

Many  eastern  and  middle  states,  such  as  Massachusetts,  Delaware, 
Georgia.  Illinois,  etc. 


PLATE  XXIX 


a,  Apatite,  Renfrew,  Canada 


b,  Barite,  Alston  Moor,  England 


CLASS  VIII.    NIOBATES,  TANTALATES 


CLASS  IX.    PHOSPHATES,  ARSENATES,  VANADATES, 
ANTIMONATES,  NITRATES 

Apatite 

Apatite  is  a  mineral  of  great  commercial  importance,  occurring 
in  metamorphic  limestones  and  in  granites  often  as  well-formed  crystals 
(No.  3551)  varying  from  microscopic  size  to  dimensions  of  a  foot  or 
more  (Plate  XXIX0) .  As  usual,  the  more  nearly  perfect  crystals  with 
well-terminated  ends  occur  in  cavities.  Their  prevailing  color  is  blue, 
green  (No.  3550),  yellow,  or  brown.  Among  the  most  beautiful 
apatite  crystals  found  are  little  limpid  hexagonal  prisms  contained  in 
crystalline  schists  in  the  St.  Gothard  and  Unter- 
sultzbachthal.  Microscopic  crystals  are  found 
in  a  variety  of  igneous  rocks.  The  planes  most 
commonly  appearing  (Fig.  222)  are  the  follow- 
ing: (1010),  (1120),  (1011),  (1121),  (oooi). 
The  prisms  are  usually  vertically  striated. 
Apatite  resembles  beryl  in  appearance,  but  is 
softer,  has  imperfect  cleavage  parallel  to  the 
base,  and  a  high,  refractive  index. 

Chemically  there  are  two  varities  of  apatite: 
the  ordinary,  which  contains  fluorine;  and  the 
less  common,  in  which  fluorine  is  replaced  by 
chlorine.  According  to  physical  condition  there 
are  two  kinds  which  are  even  more  markedly 
different  than  are  the  two  chemical  varieties.  The  first  is  pure 
crystallized  apatite,  which  is  found  filling  veins  and  as  inclusions  in 
metamorphic  rocks  (Nos.  3666,  3709,  3712).  The  second  is  phos- 
phorite (No.  4307),  the  white,  structureless  variety,  organic  in  origin 
and  occurring  in  extensive  beds  in  the  Carolinas  and  Tennessee.  It 
has  resulted  by  the  concentration  of  phosphatic  material  which  was 
previously  disseminated  through  sands  and  sandstone. 


1010 


FIG.  222. — Apatite 


176  GUIDE  TO  MINERAL  COLLECTIONS 

The  crystallized  apatite  is  found  in  most  of  the  Appalachian 
states  and  iri  the  drifts  over  the  middle  states  in  granular  limestone 
and  in  granites,  gneisses,  and  schists,  and  in  veins  in  iron  ores. 

Apatite  is  one  of  the  most  important  of  all  minerals  to  man, 
inasmuch  as  it  is  the  chief  source  of  phosphorus,  a  chemical  substance 
indispensable  to  plant  growth. 

SUMMARY 

Apatite.—  CasF(P04)3;  CaO  =  5S-5  per  cent,  P3OS=42.3  per  cent, 
F=3.8  per  cent.  Hexagonal;  symmetry  hexagonal  equatorial;  a:c= 
1:0.7346.  (101),  (1011),  (1121),  (2131).  Cleavage  parallel  to  (oooi), 
1610).  Brittle;  fracture  conchoidal. 

Hardness  =  5  ;  gravity  =3.2.  Colorless  ;  luster  vitreous  ;  transparent  ; 
w  =  i  .  646.  Double  refraction  negative,  weak  ;  w  —  c  =  o  .  004. 

Fusible  with  difficulty;  soluble  in  hydrochloric  acid. 

Ottawa  County,  Quebec,  Canada;  Bolton,  Massachusetts;  Crown 
Point,  New  York;  New  Jersey. 

Pyromorphite 

Pyromorphite  (No.  507)  is  a  lead  chloro-phosphate  found  in 
quantities  in  upper  levels  of  lead  mines,  where  it  has  been  forming 
during  the  decomposition  of  lead  sulphide.  It  was  named  pyro- 
morphite  because,  when  fused  before  the  blowpipe,  upon  cooling  it 
solidifies  with  many  facets  (irvp,  "fire";  AWP$I?>  "form").  These 
facets  are  not  true  crystal  faces.  The  true  crystals  are  composed  of 
prisms  and  basal  planes  which  produce  barrel-shaped  forms  because 
of  aggregation  and  curvature  of  the  prisms.  A  violet  color  is  shown 
by  large  hexagonal  prisms  occasionally,  but  the  prevailing  color  is 
green  or  brown. 

SUMMARY 


Pyromorphite.—  Pb5Cl(PO4)3;  PbO  =  82.3  per  cent,  P205=i5.7  per 
cent,  Cl=  2  .  6  per  cent. 

Hexagonal;  symmetry  hexagonal  equatorial.  (1010),  (1011),  (oooi). 
Cleavage  parallel  (1010),  (1011)  imperfect.  Brittle;  fracture  sub- 
conchoidal. 

Hardness  =3.  5;  gravity  =7.  Green;  luster  resinous.  Translucent; 
<o  =  i  .  50.  Double  refraction  negative  ,  weak  ;  to  —  e  =  o  .  006  . 

Easily  fusible  (1.5).     Soluble  in  nitric  acid. 

Missouri,  Wisconsin,  Colorado,  New  Mexico,  and  Australia. 


CLASS  X.    BORAXES,  URANATES 

Borax,  Colemanite,  Boracite 

These  three  borates  are  of  importance  as  the  source  of  boron 
compounds  which  are  useful  as  antiseptics,  medicines,  cosmetics, 
and  welding  compounds.  All  of  them  are  most  commonly  met  with  in 
arid  regions  in  connection  with  salt  lakes,  past  or  present.  Crystals 
of  colemanite  and  boracite  are  often  beautiful  because  of  their  trans- 
parent character  and  lustrous  surfaces. 

SUMMARY 

Borax. — Na2B4O7.ioH2O;  Na2O=i6.2  per  cent,  B2O3=36.6  per  cent, 
H2O2=47 • 2  Per  cent.  Monoclinic,  prismatic  class;  a:b:c=  i .09: i :o. 562; 
$=73°;  (I0°)>  (IIO)>  C001)*  C111)-  Cleavage  perfect  (100);  fracture 
conchoidal. 

Hardness  =  2 ;  gravity  =  1.7.  White,  vitreous,  translucent;  /3=  i .  47. 
Double  refraction  negative ;  7—  a  =  o .  004;  acute  bisectrix  normal  to  (oio) ; 
2  £=59°;  p>v. 

Fusible,  swells  up;  soluble  in  water;  sweetish. 

Thibet,  Peru,  California,  Nevada. 

Colemanite. — Ca2B60n.5H20;  CaO=27.2  per  cent,  B2O3=5o.9  per 
cent,  H2O  =21.9  per  cent.  Monoclinic,  prismatic  class ;  a:b:c=o.fj: 
1:0.541;  18=70°;  (no),  (301),  (100),  (oio),  (ooi),  (in),  (021),  (221). 
Cleavage  (o  i  o);  fracture  uneven. 

Hardness =4;  gravity  =2. 4.  Colorless,  white;  translucent,  vitreous; 
0  "-1.5902. 

Fusible,  exfoliates;  soluble  in  hot  hydrochloric  acid;  insoluble  in 
water. 

California,  Chile. 

Boracite. — Mgs(MgCl)2BI6O30;  MgO  =  31.4  per  cent,  Cl=  7 . 9  per  cent, 
B2O3=62.5  per  cent.  Dimorphous;  crystals  formed  above  265°  C., 
regular;  below  that,  orthorhombic;  (no),  (100),  (in),  (in),  (211). 
Cleavage  (in)  imperfect;  brittle;  fracture  conchoidal. 

Hardness=7;  gravity =3.  Colorless,  vitreous,  translucent.  Double 
refraction;  /?=  1.667;  T— a  =  o.on;  2  7=90°. 

Fusible,  swells  up;  soluble  in  hydrochloric  acid. 

Stassfurt,  Prussia. 

177 


178  GUIDE  TO  MINERAL  COLLECTIONS 

Uraninite 

The  uranate  uraninite  is  of  interest  because  it  is  a  source  of 
uranium,  of  radium,  and  of  helium.  Its  composition  is  doubtful, 
inasmuch  as  a  large  number  of  rare  elements  are  present.  In  addi- 
tion to  oxides  of  uranium,  thorium,  lead,  iron,  and  calcium,  small 
quantities  of  the  following  have  been  found:  zirconium,  cerium, 
lanthanum,  didymium,  yttrium,  erbium,  helium,  manganese,  sodium, 
potassium,  silicon,  phosphorus,  and  hydrogen.  Its  composition 
may  be  expressed  by  the  formula  U30g.  Uranium  compounds  are 
used  in  the  laboratory  for  the  determination  of  phosphorus  and  zinc, 
in  the  manufacture  of  pigments,  glazes,  and  special  steels. 

SUMMARY 

Uraninite. — U3Os.    Regular,     (in),     (no),     (100).     Crystals     rare, 
crystalline  masses,  botryoidal  groups.    Brittle;  fracture  conchoidal. 
Hardness  =5.5;  gravity =9.5.    Brown,  black ;  luster  dull. 
Infusible;  soluble  in  nitric  and  sulphuric  acids;  radio-active. 
Colorado,  Cornwall,  Austria. 


CLASS  XI.     SULPHATES,  CHROMATES,  TELLURATES 

Class  XI,  containing  the  sulphates,  chromates,  and  tellurates, 
is  an  outstanding  class  because  of  at  least  four  commercially  and 
scientifically  interesting  minerals,  namely,  barite,  celestite,  anglesite, 
and  gypsum. 

Barite 

Barite,  or  heavy  spar  (/3apus,  "heavy"),  so  named  since  it  is 
nearly  twice  as  heavy  as  other  white  minerals  like  calcite  or  gypsum, 
is  important  because  of  its  fine  crystals,  its  great  masses,  and  its 
usefulness. 


FIG.  224. — Barite 


no    ~^J—  "I 


FIG.  223. — Barite  FIG.  225. — Barite 

The  crystals  are  usually  flat  (Nos.  3562  and  3556),  and  consist 
of  large  basal  planes  with  short  prisms,  as  in  Figure  223.  Forms 
composed  of  dome  planes  elongated  parallel  to  the  a  axis  (Fig.  224) 
are  not  uncommon  (No.  4060).  Cleavage  pieces  take  the  form  of 
Figure  225,  and  the  position  of  the  axes  is  indicated  by  the  cleavage, 
which  usually  shows  pearly  cracks.  Prismatic  cleavage  is  good. 
Aggregates  of  crystals  produce  rounded  masses  from  which  acute 
prism  edges  protrude.  Radiated,  columnar,  and  massive  (No.  3559) 
forms  are  common,  though  a  white,  earthy,  massive  condition  is  most 
characteristic.  Discoloration  by  iron  is  usual. 

Inorganic  phosphorescence  was  first  discovered  when  an  Italian 
investigator  in  the  early  part  of  the  seventeenth  century  heated 

179 


i8o  GUIDE  TO  MINERAL  COLLECTIONS 

barite  on  charcoal  and  noticed  that  in  the  dark  it  continued  to  emit 
a  glow,  due  to  the  reduction  of  the  sulphate  to  sulphide. 

Barite  is  found  in  veins  and  masses  with  ores  oi  lead,  antimony, 
and  iron  in  limestones,  especially  in  Georgia,  Missouri,  and  Tennessee. 

It  is  used  in  the  manufacture  of  white  paint,  filler  for  paper, 
barium  for  chemical  and  medicinal  uses,  etc.  Nearly  four  hundred 
thousand  dollars'  worth  of  barite  was  produced  in  the  United  States 
in  1915. 

SUMMARY 


Barite.  —  BaSO4;  BaO  =  65.7  per  cent,  $03=34.3  per  cent.-  Ortho- 
rhombic;  a:b:c=o.  815:1:1.  314.  (ooi),  (no),  (102),  (on),  (122),  (in). 
Cleavage  parallel  (no)  and  (ooi)  perfect;  brittle;  fracture  uneven. 

Hardness  =  3  ;  gravity  =4.5.  Colorless  ;  luster  vitreous  ;  transparent  ; 
18=1.637.  Double  refraction  positive,  strong;  7—  a  =  o.oi2.  Axial  plane 
(oio);  acute  bisectrix  perpendicular  to  (  i  oo);  2^=64°;  p<v. 

Fusible  (3)  with  decrepitation;  insoluble  in  acid. 

Georgia,  Missouri,  Tennessee,  Kentucky. 

Celestite 

The  next  member  of  the  group  is  the  strontium  sulphate,  celestite, 
so  named  (coelestinus,  "blue")  since  the  first  crystals  discovered  (in 

Pennsylvania)  exhibited  delicate 

V*  blue  shades,  due,  no  doubt,  to 

o  the    presence   of   traces   of   iron 

phosphate.    The  crystals  are  in- 
-  f        dosed   by  a  variety  of   planes. 
While  barite   is   more   often 
elongated  along  the  a  axis,  the 
elongation  of  celestite  takes 
place  parallel  to  the  b  axis.     The 
FIG.    226—  Celestite    (ooi),    (104),      massive    forms   are   common   in 
(102),  (no),  and  (on).  limestone,   marl,  sandstone,  and 

beds  of  gypsum. 

Sicily;  Strontian,  Scotland;  North  Bass  Island,  Lake  Erie; 
Pennsylvania,  Kansas,  Texas,  West  Virginia,  and  Tennessee  contain 
supplies  of  this  mineral,  which  together  with  strontianite  are  the 
chief  sources  of  strontium  nitrate,  a  compound  much  used  to  produce 
the  crimson  colors  in  fireworks. 


SULPHATES,  CHROMATES,  TELLURATES  181 

SUMMARY 

Celestite. — SrS04 ;  SrO  =  56 . 4  per  cent,  SO3 = 43 . 6  per  cent. 

Orthorhombic;  a:b:c=o. 779:1:1. 280.  (ooi),  (no),  (on),  (102), 
(104).  Cleavage  parallel  (ooi)  perfect;  parallel  (no)  good.  Brittle; 
fracture  uneven. 

Hardness = 3 ;  gravity =3.9.  Colorless ;  luster  vitreous ;  transparent ; 
ft  =1.624.  Double  refraction  positive,  weak;  7—0  =  0.009.  Axial  plane 
parallel  (oio).  Acute  bisectrix  perpendicular  to  (100).  2  £  =  88°  38'. 

Fusible  (3)  with  decrepitation.    Insoluble  in  acids. 

Lake  Erie,  Pennsylvania,  New  York,  Kansas,  Texas,  West  Virginia, 
Tennessee. 

Anglesite 

Lead  sulphate  (PbSO4)  crystals  resemble  barite  and  celestite  in 
being  flat  (No.  3563).  They  are  elongated  not  only  parallel  to  the 
b  axis  but  also  quite  commonly  parallel  to  the  c.  They  were  first 


102 

FIG.  227.— Anglesite  FIG.  228.— Anglesite 

found  on  the  island  of  Anglesy,  and  many  localities  now  furnish  fine, 
lustrous,  transparent,  colorless  crystals  which  line  the  cavities  in 
glistening,  granular  galena.  The  lead  mines  of  Missouri,  Wisconsin, 
Kansas,  Colorado,  Mexico,  and  Australia  furnish  this  mineral  in 
massive  varieties  and  in  such  quantities  as  to  render  it  an  important 
ore  of  lead. 

Its  easy  fusibility  (1.5),  adamantine  luster,  and  great  weight 
(gravity,  6.3)  render  it  easy  of  determination. 

SUMMARY 

Anglesite. — PbSO4 ;  PbO = 73 . 6  per  cent,  SO3  =  26.4  per  cent.  Ortho- 
rhombic;  a:b:c=o. 785: 1 11.289.  (no),  (ooi),  (on),  (102),  (104),  (122), 
(in),  cleavage  parallel  (no)  and  (ooi)  fair.  Brittle;  fracture  conchoidal. 


182 


GUIDE  TO  MINERAL  COLLECTIONS 


Hardness  =  3;  gravity =3. 6.  Colorless;  luster  adamantine;  trans- 
parent; ^8=1.883.  Double  refraction  positive,  strong;  y— a  =  o.oi6. 
Axial  plane  parallel  (oio).  Acute  bisectrix  perpendicular  to  (100). 
2  #  =  89°  52';  p<v. 

Easily  fusible  (1.5).     Soluble  in  nitric  acid  with  difficulty. 

Missouri,  Wisconsin,  California,  Mexico,  and  Australia. 


Barite,  celestite,  and  anglesite  constitute  a  fine  example  of  an 
isomorphous  group,  with  simple,  bright,  glassy,  tabular  or  prismatic 
orthorombic  crystals  which  cleave  parallel  to  the  base  (ooi)  and 
prism  (no).  The  optical  characteristics  are  all  similar. 

Gypsum 

The  next  sulphate  of  importance  is  the  hydrated  calcium  sulphate 
gypsum.     This  is  a  mineral  vastly  more  abundant  than  all  the  other 
members  of  the  group  combined.     The  name  gypsum  was  used  by 
the  Greeks  (yv\f/o$).     Dioscorides  and  Pliny 
called  it  "selenites,"  from  which  our  word 
"  selenite  "  is  derived,  which  is  now  restricted 


FIG.  229. — Gypsum 


FIG.  230. — Gypsum 


FIG.  231. — Gypsum 


to  lustrous,  satiny,  crystallized  gypsum.  Near  Paris  (Montmartre) 
gypsum  was  early  quarried,  ground,  and  burned  for  plaster  and  hence 
was  named  plaster  of  Paris.  When  used  upon  the  fields -as  a  fertilizer 
it  is  called  land  plaster.  When  translucent,  compact,  and  suitable 
for  carving,  it  is  called  alabaster.  Satin  spar  is  composed  of  compact 
fibers,  with  the  luster  of  satin,  and  is  used  for  cheap  jewelry.  It  is 


PLATE  XXX 


Gypsum,  showing  fishtail  twin  and  curled  form 


PLATE  XXXI 


Gypsum,  "selenite,"  Wayne  County,  Utah 


SULPHATES,  CHROMATES,  TELLURATES 


183 


easy  to  work  but  even  more  easy  to  destroy,  since  it  is  so  soft  that  it 
has  slight  value. 

The  chief  use  of  gypsum,  however,  is  as  plaster  of  Paris.  When 
ground  and  burnt,  it  loses  its  water  of  crystallization,  then  upon 
being  mixed  with  water  again  it  takes  up  the  lost  molecules,  and 
recrystallizes  or  "sets"  (CaSO4-H2O). 

The  greatest  quantities  are  now  mined  in  Michigan  (No.  3523), 
New  York,  Virginia,  Ohio,  Iowa,  Alabama,  Arkansas.  For  hundreds 


FIG.    232. — Gypsum,     twinned 
juxtaposition  parallel  (100). 


by 


FIG.     233. — Gypsum,     twinned 
interpenetration  parallel  (100). 


by 


of  miles  beds  of  gypsum  may  be  seen  stretching  like  a  white  ribbon 
over  the  country  in  Wyoming,  Colorado,  and  many  other  Cordilleran 
states. 

Crystals  sometimes  several  feet  long  are  found  (No.  4058).  In 
Utah  a  few  years  ago  a  huge  geode  was  discovered  whose  walls  were 
covered  with  gigantic  transparent  crystals.  Many  of  them  now 
adorn  the  museums  of  this  and  other  countries  (Nos.  3890,  4308, 
4498)  (Plate  XXXI).  Multitudes  of  excellent  crystals  have  been 
obtained  at  Girgenti,  Sicily  (No.  3567);  Bex,  Switzerland;  Mont- 
martre,  France;  Oxford,  England  (No.  3535).  See  Figures  229  to 
233.  Large  transparent  crystals  from  Kansas  and  Colorado,  imper- 
fect in  outline,  yield  beautiful  cleavage  pieces.  The  cleavage  parallel 
to  the  clinopinacoid  (oio)  is  so  perfect  that  plates  of  any  desired 
thickness  may  be  obtained  and  used  under  a  microscope  to  detect 


184  GUIDE  TO  MINERAL  COLLECTIONS 

the  weak  double  refraction  of  some  minerals.  For  example,  if  a 
plate  of  such  thickness  as  to  yield  red  of  the  first  order  between 
crossed  nicols  is  used,  it  will  become  blue  when  the  thin  section  under 
examination  is  positive  (since  gypsum  is  positive).  In  this  case  the 
color  is  raised.  It  becomes  yellow,  that  is,  depressed,  when  the 
mineral  is  negative. 

There  are  two  other  cleavages  also,  one  with  a  fibrous  surface 
parallel  to  an  orthodome  (ioi),  and  one  with  conchoidal  surface 
parallel  to  the  orthopinacoid  (100).  Cleavage  lines  aid  in  orienting 
crystals  that  are  without  crystal  faces. 

Twinning  is  parallel  to  the  orthopinacoid  (100)  both  by  juxta- 
position (Fig.  232)  and  by  interpenetration  (Fig.  233).  The  fibrous 
cleavage  cracks  parallel  to  the  orthodome  do  not  run  uniformly 
across  the  crystal,  but  meet  at  an  angle  of  47°5o'  on  the  line  of  contact. 

The  crystals  are  often  curved  or  lenticular.     (See  Plate  XXX.) 

SUMMARY 

Gypsum.— CaSO4-2H20;  CaO=32.5  per  cent,  SO3=46.6  per  cent, 
H3O=2O.9  per  cent.  Monoclinic;  0:6:^=0.690: 1:0.412.  /?=8o°42'. 
(oio),  (in),  (no),  (130),  (103).  Twinned  on  (100),  also  on  (101).  Cleav- 
age parallel  (oio)  perfect;  parallel  (100)  and  (101)  imperfect;  parallel 
(100)  and  (101)  imperfect.  Sectile;  flexible. 

Hardness  =  2;  gravity  =2. 3.  Colorless;  luster  vitreous;  transparent; 
/?=i.522.  Double  refraction  positive;  y— a  =  o. oio.  Axial  plane  parallel 
(oio).  Acute  bisectrix  inclined  37°  30'  to  the  normal  of  (100),  and  43°  12' 
to  the  normal  of  (ooi).  2  £  =  95°.  p>v.  Inclined  dispersion. 

Easily  fusible  (3) .     Soluble  in  hydrochloric  acid. 

Michigan,  New  York,  Virginia,  Ohio,  Iowa,  Alabama,  Arkansas,  and 
the  Cordilleran  states. 


CLASS  XII.    TUNGSTATES,  MOLYBDATES 


100 


no 


The  class  of  tungstates  and  molybdates  contains  but  few  min- 
erals and  those  few  are  of  slight  importance.  One  example  of  each 
may  be  considered:  the  tungstate,  wolframite;  and  the  molybdate, 

wulfenite. 

Wolframite 

Wolframite  (No.  3533),  a  black  mineral  accompanying  cassiterite 
in  tin-bearing  regions,  and  greatly  resembling  cassiterite  in  appear- 
ance, is  the  chief  source  of  tungsten,  an  element  being  used  in  an 
increasing  degree  in  manufactures.  Well-formed  monoclinic  crystals 
resembling  those  shown  in  Figure'  234  are  common,  but  bladed, 
lamellar,  or  granular  forms  are  more  abun- 
dant. Its  perfect  cleavage  parallel  to  (oio) 
and  its  stibnite-like  luster  aid  in  distinguishing 
it,  although  otherwise  it  is  a  somewhat  diffi- 
cult mineral  to  identify,  since  blowpipe  re- 
actions for  tungsten  are  masked  by  the 
presence  of  the  iron  and  manganese  in  its 
formula,  (FeMn)WO4.  After  wolframite  is 
boiled  in  aqua  regia,  tungstic  oxide  appears  as 
a  yellow  residue. 

Tungsten  steel  is  especially  valuable  for 
permanent  magnets,  cutting  tools,  wires  for 

electric  purposes,  etc.    Tungsten  is  also  used  as  a  dye  which  renders 
cotton  less  inflammable. 

Wolframite  is  found  in  veins  in  Cornwall,  Zinnwald,  Black  Hills, 
North  Carolina,  and  Missouri. 

SUMMARY 

Wolframite. —  (FeMn)WO4;  FeO  varying  from  2  to  19  per  cent, 
MnO  from  6  to  22  per  cent,  WO3  =  76  per  cent.  Monoclinic;  holosym- 
metric.  Cleavage  parallel  (oio)  perfect,  parallel  (100)  imperfect.  Brittle; 
fracture  uneven. 

Hardness  =  5. 5;  gravity  =7. 3.  Black;  streak  reddish  brown;  luster 
metallic;  opaque. 

Fusible  (3)  to  magnetic  bead.     Decomposed  by  hydrochloric  acid. 

North  Carolina,  Missouri,  South  Dakota. 

185 


FIG.  234. — Wolframite 


i86 


GUIDE  TO  MINERAL  COLLECTIONS 
Wulfenite 


This  molybdate  (Nos.  3528  and  3531),  PbMoO4,  is  a  heavy,  red, 
resinuous  mineral  which  occurs  in  granular  masses,  and  often  in  thin, 
tabular,  square  crystals  (Fig.  235),  or 
less   commonly    in    acute    pyramids 
(Fig.  236).     Were  it  not  so  brittle  and 
soft,   it  would  be  one  of  the  most 


FIG.  235. — Wulfenite 


FIG.  236.— Wulfenite 


prized  of  gems,  since  it  is  beautiful  in  color  and  has  a  high  luster. 
Commercially  it  is  of  small  value  because  of  its  rarity. 

SUMMARY 

Wulfenite.— PbMoO4;  PbO  =  6o.7  per  cent,  MoO3  =  39.3  per  cent. 
Tetragonal;  symmetry,  tetragonal  polar.  0:^=1:1.577.  (ooi),  (102), 
(in),  (320).  Cleavage  parallel  (in)  good.  Brittle;  fracture  sub- 
conchoidal. 

Hardness  =  3 ;  gravity =6.7.  Red ;  streak  white ;  luster  adamantine ; 
translucent;  o>  =  2.402.  Double  refraction  negative,  strong;  (0—6  =  0.098. 

Easily  fusible  (2) ;  soluble  in  hydrochloric  acid. 

Arizona,  New  Mexico,  California,  Missouri,  Pennsylvania. 


CLASS  XIII.     ORGANIC  ACID  SALTS 

The  organic  acid  salts,  oxalates  and  mellates,  which  constitute 
Class  XIII  are  rare  and  unimportant,  hence  we  may  pass  at  once  to 
the  next  class. 


CLASS  XIV.    HYDROCARBONS 

Though  the  members  of  this  class  are  all  of  organic  origin,  yet 
they  have  been  so  changed  .by  the  loss  of  some  constituent  as  to  rank 
as  mineral  substances.  Several  of  them  are  amorphous.  Others 
retain  the  structure  of  the  substance  from  which  they  were  derived. 
Some  of  them  may  be  most  properly  classified  as  rocks,  but  since 
they  constitute  part  of  a  series  they  are  here  included.  The  most 
abundant  representatives  are  the  fossil  resins,  asphalt,  heavy  and 
light  oils,  gas,  and  coal. 

Fossil  Resins 

Amber  is  a  fossil  resin  occurring  in  amorphous  masses  which  vary 
in  size  from  small  grains  or  droplets  to  chunks  a  foot  or  more  in 
diameter.  It  was  exuded  from  ancient  conifers  or  leguminous  trees, 
and  buried  by  drifting  sands  in  recent  geological  formations  in  Spain, 
Sicily,  Germany,  etc.  It  is  characterized  by  conchoidal  fracture, 
softness  (hardness,  2),  low  specific  gravity  (gravity,  i.i),  yellowish 
to  brown  color,  greasy  luster,  and  translucency.  It  shows  fluo- 
rescence, is  negatively  electric,  melts  at  about  287°  and  burns  with 
a  bright  flame  and  an  agreeable  odor.  It  is  composed  of  carbon, 
hydrogen,  and  oxygen  (C^H^At);  C  =  78.93  per  cent,  H  =  io.55  per 
cent,  0  =  10.52  per  cent.  It  is  used  in  the  manufacture  of  buttons, 
beads,  pipestems,  varnish,  amber  oil,  and  acid. 

Copal  is  a  kind  of  amber  which  contains  a  larger  proportion  of 
hydrogen  and  melts  at  a  lower  temperature  (210°).  It  is  slightly 
harder  than  amber  (hardness,  2.5).  It  is  the  dried  sap  of  leguminous 
and  coniferous  trees  which  are  found  in  many  parts  of  the  world,  such 
as  New  Zealand,  Australia,  Madagascar,  the  east  and  west  Coasts  of 

187 


i88  GUIDE  TO  MINERAL  COLLECTIONS 

Africa,  and  various  places  in  South  America.  Nine-tenths  of  the 
copal  used  is  obtained  from  deposits  buried  sometimes  as  deeply  as 
twenty  feet  and  often  no  doubt  thousands  of  years  old. 

All  varieties  of  amber  are  used  chiefly  as  material  from  which  to 
manufacture  varnish.  Insects  imprisoned  in  the  gum  as  it  was 
exuding  from  trees  have  been  preserved  with  remarkable  fidelity,  so 
that  not  only  are  their  most  delicate  membranes  intact,  but  in  many 
cases  an  idea  of  the  original  color  can  be  obtained. 

'    Asphalt 

This  hydrocarbon  is  of  indefinite  composition.  It  is  black, 
burns  with  a  pitchy  odor  and  is  slightly  heavier  than  water  (gravity, 
i  .1;  hardness,  2).  It  melts  at  100°  C.  and  ignites  readily  with  black 
smoke  and  bright  flame.  At  a  sufficiently  low  temperature  it  shows 
conchoidal  fracture.  It  is  soluble  in  ether. 

It  occurs  in  beds  or  lakes  in  the  island  of  Trinidad  and  in  veins 
or  disseminated  through  sandstone  or  limestone  in  Kentucky,  Cali- 
fornia, etc. 

It  forms  one  of  the  most  satisfactory  paving  materials  when 
mixed  with  sand  and  broken  limestone.  It  is  used  for  roofing,  for 
calking  material  on  ships,  for  paint  on  metal  and  woodwork,  and  as  an 
adulterant  of  rubber  goods. 

Petroleum 

Petroleum  is  one  of  the  most  important  of  mineral  substances, 
being  second  only  to  coal  and  iron  in  the  contribution  which  it  yearly 
makes  to  the  wealth  of  mankind.  It  has  been  found  in  many  coun- 
tries, but  nowhere  so  extensively  as  in  the  United  States.  It  occurs 
in  strata  from  the  Ordovician  to  the  Pleistocene.  It  has  been 
produced  by  the  distillation  under  great  pressure  of  both  animal  and 
vegetable  substances. 

Petroleum,  or  "rock  oil,"  is  composed  of  a  variety  of  oils,  form- 
ing a  series  from  the  volatile  and  easily  flowing  oils  to  viscous  oils, 
lubricating  oils,  and  greases.  It  consists  chiefly  of  the  paraffines 
(CnH2n+2)  in  Pennsylvania  and  of  the  naphthenes  (C6HI2)  in  the 
Caucasus.  The  color  varies  from  dark  brown  to  greenish,  and  the 
gravity  from  0.7  to  0.9.  Petroleum  shows  a  distinct  fluorescence. 

Benzine,  naphtha,  gasoline,  kerosene,  lubricating  oil,  vaseline,  dye- 
stuffs,  and  other  chemicals  are  derived  from  petroleum. 


HYDROCARBONS  189 

Pennsylvania  long  held  chief  place  in  the  production  of  petroleum, 
but  recently  California  has  surpassed  her,  and  Ohio,  Indiana, 
Illinois,  Kansas,  Oklahoma,  and  Texas  have  all  shown  remarkable 
pools.  Mexico  and  the  Caucasus  are  increasing  in  productiveness. 

Natural  Gas 

Closely  associated  with  petroleum  and  having  the  same  origin  is 
natural  gas.  It  too  consists  mainly  of  the  lower  paramne  methane 
(CH4)  and  ethane  (CH3),  and  also  carbon  monoxides,  carbon  dioxide, 
hydrogen,  neon,  and  the  new  gas.helium,  so  necessary  for  war  balloons. 

Coal 

Coal  consists  of  solid  hydrocarbons  derived  from  vegetable 
growths  of  former  geological  ages.  Trees,  shrubs,  weeds,  mosses,  and 
especially  spores  of  cryptogams  contributed  to  its  formation.  More 
than  five  hundred  different  species  of  plants  have  been  identified 
among  those  concerned  in  the  production  of  coal.  Among  them  are 
six  species  of  algae;  two  hundred  and  fifty  species  of  ferns;  eighty- 
three  species  of  lycopods,  that  is,  club  mosses  whose  powder  is  used 
for  fireworks,  medicines,  etc. ;  thirteen  species  of  equisetites,  that  is, 
rushes,  horsetails,  etc.;  sixty  sigillarids,  whose  trunks  were  ribbed 
and  scarred  like  giant  cacti;  twelve  species  of  noggerathia  with  over- 
lapping scales  on  their  trunks  and  pinnate  leaves;  forty-four  astero- 
phyllites;  and  three  species  of  cycads,  the  sago  palms. 

All  of  the  above  were  acotyledons,  the  lowest  form  of  vegetable 
life.  They  comprise  five-sixths  of  all  the  plants  which  have  been 
identified  in  coal.  The  remaining  one-sixth  were  fifteen  species  of 
coniferous  trees  and  fifteen  of  the  palms.  All  of  the  above-named 
species  are  similar  to  vegetation  which  thrives  in  a  warm,  moist 
climate  today.  These  plants,  grown  in  swamps  or  near  lakes  and 
rivers,  were  deposited  in  beds,  buried  under  mud  that  later  turned 
to  stone,  and  by  the  loss  of  hydrogen  and  oxygen  were  converted 
into  coal. 

Cross-sections  of  coal  fields  in  all  parts  of  the  country  point  to 
such  a  history.  At  the  bottom  of  a  coal  field  occurs  a  conglomerate 
such  as  would  form  on  a  new  shore  line.  This  is  covered  by  sandstone 
that  indicates  long  action  of  the  waves  and  gradual  decrease  in  their 
severity.  Next  comes  shale,  and  then  clay,  "fire  clay,"  such  as  would 
be  formed  in  the  shallow  waters  of  ponds  into  which  sluggish  streams 


I  go  GUIDE  TO  MINERAL  COLLECTIONS 

carry  silt.  These  are  followed  by  the  coal  from  a  few  inches  to  several 
feet  in  thickness,  such  as  might  be  formed  in  a  peat  swamp.  The 
lowest  coal  bed  in  Illinois  is  called  coal  No.  i.  This  is  covered  by 
gray  shale  showing  subsidence  of  the  swamp  and  burial  under  mud: 
Further  subsidence  brought  conditions  favorable  to  formation  of 
sandstone.  Re-elevation  introduced  other  shale  and  fire-clay  forma- 
tions which,  in  their  turn,  were  followed  by  swamps  in  which  coal 
No.  2  was  formed.  This  shifting  of  the  shore  line  was  repeated 
many  times  in  some  localities,  as  is  indicated  not  only  by  the  differ- 
ent coal  seams  but  also  by  their  containing  rocks.  There  are  a  dozen 
different  beds  in  Illinois. 

Mollusks,  fishes,  and  amphibians  buried  in  these  deposits  and 
changed  to  stone  give  further  light  upon  the  history  of  coal. 

Coal  is  found  in  five  geological  systems,  from  the  middle  Tertiary 
down  through  the  upper  Cretaceous,  the  lower  Jurassic  (Oolite),  and 
the  Triassic  to  the  Carboniferous.  Of  these  systems  the  Carbonif- 
erous far  surpasses  all  others  in  production. 

In  America  there  are  seven  extensive  coal  regions.  The  first  is 
that  included  in  Acadia,  Nova  Scotia,  New  Brunswick,  and  Rhode 
Island.  The  coal  measures  of  Nova  Scotia  are  7,000  feet  thick  and 
contain  76  seams.  In  Rhode  Island  and  Massachusetts  a  graphitic 
anthracite  is  found. 

The  second  region,  covering  70,000  square  miles  along  the  Appa- 
lachians, includes  the  famous  coal  fields  of  Pennsylvania,  Ohio,  Mary- 
land, Virginia,  West  Virginia,  Kentucky,  Tennessee,  and  Alabama. 
In  some  portions  of  this  field  the  coal  measures  are  4,000  feet  thick. 
From  no  region  of  the  world  has  more  or  better  anthracite  and 
bituminous  coal  been  obtained. 

The  third  field  occupies  about  7,000  square  miles  in  Michigan, 
where  the  productive  Carboniferous  is  but  about  300  feet  thick. 
Indiana  and  Illinois,  with  approximately  1,000  feet  of  Carboniferous 
strata  covering  58,000  square  miles,  comprise  the  fourth  field — one  of 
the  most  actively  worked  and  most  remunerative. 

At  one  time,  continuous  with  this  field  was  that  which  now  con- 
stitutes the  fifth  field,  covering  94,000  square  miles.  It  is  found  in 
Iowa,  Missouri,  Arkansas,  and  Texas.  Here  the  Carboniferous  rocks 
are  thicker  than  in  any  other  portion  of  America  but  not  for  that 
reason  more  promising. 


HYDROCARBONS  191 

The  sixth  region  is  one  of  scattered  character,  occurring  chiefly 
in  Montana,  Wyoming,  Colorado,  Utah,  and  Arizona.  On  the  Pacific 
Coast  is  the  seventh  region,  embracing  Washington,  Oregon,  and  Cali- 
fornia. Altogether  there  are  more  than  335,000  square  miles  of  known 
coal-bearing  territory  in  North  America. 

The  anthracite  area  covers  less  than  1,000  square  miles.  Half  of 
this  is  in  Massachusetts  and  Rhode  Island,  where  the  anthracite  is 
almost  without  fuel  value  because  of  its  graphitic  character  and  con- 
sequently no  production  has  been  reported  in  recent  years.  Colorado 
contains  15  square  miles.  Pennsylvania  has  a  field  covering  470 
square  miles.  From  this  latter  region  practically  all  the  anthracite 
produced  in  the  United  States  is  obtained.  The  total  coal  produc- 
tion in  the  United  States  in  1915  was  valued  at  six  hundred  and 
eighty-six  million  dollars.  More  than  a  thousand  million  tons  of 
coal  are  used  in  the  world  each  year,  and  of  this  amount  the  United 
States  furnishes  the  greatest  part.  Before  the  world-war  Great 
Britain  came  next  in  production,  followed  in  descending  order  by 
Germany,  Austro-Hungary,  France,  Belgium,  Russia,  Japan,  India, 
Canada,  New  South  Wales,  Spain,  South  African  Republic,  and  New 
Zealand. 

Coal  was  first  used  in  London  in  1240.  After  people  had  been 
using  it  for  sixty-six  years  a  law  was  passed  against  it  on  account  of 
the  smoke,  which  was  declared  to  spoil  ladies'  complexions  and 
clothes!  As  early  as  1552  men  began  to  fear  all  the  coal  in  the 
world  would  soon  be  exhausted!  In  1698  the  first  mention  of  coal 
in  the  United  States  was  made  by  Father  Hennepin  as  occurring  near 
Fort  Creve  Coeur  on  the  Illinois  River  near  the  place  where  Peoria 
now  stands.  Anthracite  was  discovered  in  Rhode  Island  in  1760. 
Being  graphitic  in  character  it  was  not  used,  and  even  the  excellent 
variety  which  occurs  in  Pennsylvania  lay  unutilized  for  forty  years 
after  its  presence  was  known.  All  early  use  of  coal  was  very  local 
owing  to  lack  of  transportation,  but  with  the  advent  of  coal,  trans- 
portation and  the  growth  of  cities  became  a  possibility. 

As  society  is  now  constituted,  no  mineral  substance  could  be 
spared  with  greater  difficulty,  and,  in  fact,  without  coal  modern  civili- 
zation would  be  impossible.  Railroads,  steamships,  and  great  manu- 
facturing plants  would  disappear.  Men  would  miserably  perish  in 
winter's  cold  or  all  be  driven  to  the  tropics. 


192 


GUIDE  TO  MINERAL  COLLECTIONS 


PQ 


g 


&.J2 


PQ 


3.1 


V)  If) 

MM 


fi   3 


*3oCJCJCJc^P-iOU 

3  - 


HYDROCARBONS 


193 


One  pound  of  coal  in  a  good  engine  will  produce  six-horse-power 
for  one  hour.  One  ton  will  produce  thirteen-thousand-horse-power; 
and  since  some  railroads  use  ten  thousand  tons  per  day,  they  have 
the  equivalent  of  the  work  of  one  hundred  and  thirty  million  horses 
for  one  hour — without  the  necessity  of  feeding  the  horses.  It  is 
estimated  that  one  pound  of  coal  can  produce  as  many  foot  pounds 
of  energy  as  one  man  in  one  day.  Three  hundred  pounds  will  furnish 
as  much  power  as  one  man  per  year.  Then  if  half  the  coal  produced 
in  the  United  States  in  1915  were  used  as  a  source  of  power,  it  could  do 
.the  work  of  sixteen  hundred  million  men.  This  furnishes  one  expla- 
nation of  the  remarkable  growth  in  wealth  of  the  United  States  in 
the  last  fifty  years — a  growth  which  has  not  been  equaled  before  in 
the  history  of  the  world.  In  using  coal  so  lavishly  we  are  drawing 
on  the  energy  stored  in  the  earth  by  the  slow  growth  and  trans- 
formation of  a  succession  of  swamps  and  forests  requiring  the  sun- 
shine of  millions  of  years.  The  disappearance  of  the  coal  supply  is 
but  a  question  of  time.  In  less  than  300  years  workable  coal  seams 
will  probably  be  exhausted  in  Europe.  Those  in  other  parts  of  the 
world  will  last  longer.  But  coal  producers  and  users  should  seek  to 
avoid  the  wasteful  methods  which  at  present  prevail  in:  (i)  mining, 
(2)  removal,  and  (3)  in  use  in  furnace,  stove,  and  fireplace. 

The  following  table  shows  the  typical  proportions  of  carbon, 
hydrogen,  oxygen,  and  nitrogen  in  the  transformation  of  wood  to 
anthracite. 

CHEMICAL  CHANGES  IN  TRANSFORMATION  OF  WOOD  TO  COAL 


Carbon 

Hydrogen 

Oxygen  and 
Nitrogen 

Wood  

CQ 

6 

A.1 

Peat  

C.Q 

6 

*to 

•22 

Lignite  

60 

52 

oo 

or 

Bituminous  coal  

82 

5" 

12    2 

Anthracite  coal  

nc 

2    1 

2    ? 

SUMMARY 

Having  proceeded  thus  far,  the  visitor  to  the  museum  has  made 
the  acquaintance  of  about  100  different  minerals.  Many  more  are 
worthy  of  his  interest  and  attention;  yet  this  number  is  sufficient  to 
give  an  idea  of  the  minerals  which  constitute  the  world,  and  which 
are  used  by  man  for  ornament,  for  medicine,  as  the  source  of  metal, 
for  building  material,  and  in  many  other  ways. 

Such  a  study  furnishes  results  similar  to  those  which  would  be 
obtained  by  a  student  of  human  society  who  went  into  a  community 
of  some  1,200  inhabitants  and  made  the  acquaintance  of  100  differ- 
ent people  engaged  in  different  occupations,  holding  different  respon- 
sibilities, and  showing  varied  attainments.  One  who  has  finished 
such  a  study  would  have  a  fair  idea  of  the  whole  community. 

So  one  who  has  passed  through  the  museum,  noting  carefully  the 
minerals  shown  and  giving  attention  to  their  physical  and  chemical 
laws,  their  geography,  geology,  and  relation  to  human  activities,  has 
a  good  idea  of  the  whole  mineral  world.  It  is  not  necessary  for  him 
to  study  all  the  thirteen  hundred  different  species  and  varieties  of 
minerals.  However,  for  one  who  wishes  to  go  farther,  a  compre- 
hensive list  of  minerals  is  given  on  pages  202  to  275;  and  for 
further  study  he  is  referred  to  the  books  listed  on  page  200. 

No  country  is  better  supplied  with  minerals  than  the  United 
States,  and  few  countries  make  as  good  use  of  their  resources  in  this 
regard  as  we  do.  The  world-war  resulted  in  stimulating  mineral 
production  in  this  country.  For  a  number  of  minerals  we  had  been 
accustomed  to  go  to  foreign  countries;  for  antimony  we  had  gone  to 
China,  for  chromium  to  New  Caledonia,  for  graphite  to  Ceylon,  for 
magnesite  to  Greece,  for  manganese  and  platinum  to  Russia,  for 
sulphur  to  Sicily,  for  tin  to  Singapore,  for  vanadium  to  Peru.  But 
with  increased  difficulty  of  ocean  transportation,  prospectors  and 
producers  became  increasingly  active  in  the  search  for  and  the  mining 
of  these  minerals.  So  the  time  is  near  at  hand  when  the  United 
States  may  be  nearly  independent  in  regard  to  the  minerals  necessary 
for  the  activities  of  its  people. 

194 


SUMMARY  195 

In  1915  the  total  wealth  added  to  the  country  by  our  minerals 
was  two  billion  three  hundred  and  ninety-three  million  dollars. 

New  minerals  and  chemical  substances  are  being  constantly  dis- 
covered, and  with  their  discovery  new  ideas  and  inspiration  is  gained 
by  advanced  workers  in  various  departments  of  science.  Most 
prominent  among  recent  advances  are  those  which  have  been  made 
by  men  studying  the  ultimate  constitution  of  matter. 


NAMES  OF  MINERALS 

Among  the  minerals  which  we  have  seen,  the  name  of  one  at 
least,  kaolinite,  is  of  Chinese  origin;  two  are  of  Singhalese  origin: 
corundum  and  tourmaline;  three  are  of  Arabic  origin:  marcasite, 
amber,  and  talc.  Bismuth,  zincite,  and  hornblende  are  taken  directly 
from  the  German;  while  gold,  silver,  and  iron  are  old  Anglo-Saxon 
words. 

Many  minerals  are  named  after  some  geographical  locality,  such 
as  aragonite,  anglesite,  labradorite,  muscovite,  strontianite,  tremolite. 

Others  are  named  after  men  distinguished  in  the  science  of  mineral- 
ogy or  otherwise — biotite,  dolomite,  goethite,  franklinite,  magnesite, 
magnetite,  proustite,  smithsonite,  tennantite,  witherite. 

A  still  larger  number  were  derived  from  the  Latin  language:  sul- 
phur, antimony,  platinum,  mercury,  stibnite,  argentite,  erubesite, 
tetrahedrite,  sylvite,  fluorite,  cassiterite,  rutile,  spinel,  cerussite, 
mangenite,  albite,  enstatite,  actinolite,  garnet,  celestite,  asphalt. 

And  finally,  a  still  larger  number  of  mineral  names  originate  from 
the  Greek:  diamond,  graphite,  copper,  molybdenite,  galena,  chalco- 
cite,  sphalerite,  cinnabar,  pyrrhotite,  chalcopyrite,  pyrite,  arseno- 
pyrite,  pyrargyite,  halite,  cryolite,  chalcedony,  cuprite,  hematite, 
chromite,  pyrolusite,  limonite,  calcite,  siderite,  rhodochrosite,  mala- 
chite, azurite,  orthoclase,  microcline,  oligoclase,  anorthite,  hypersthene, 
pyroxene,  diopside,  augite,  rhodonite,  barite,  gypsum. 


196 


THE  USES  OF  MINERALS 

Minerals  contribute  toward  the  welfare  of  mankind  in  manifold 
ways.  Many  of  the  harder,  more  brightly  colored,  or  highly  refract- 
ing minerals  since  earliest  times  have  been  used  as  objects  of  personal 
adornment,  and  today  among  the  most  prized  of  all  material  objects 
are  such  minerals  as  diamonds,  rubies,  sapphires,  emeralds,  aqua- 
marine, amethyst,  agates,  turquoise,  tourmaline,  olivene,  rhodonite, 
and  malachite. 

The  metals,  together  with  their  sulphides,  oxides,  carbonates, 
and  silicates,  play  a  weighty  role  in  the  life  of  men  of  all  races  and  all 
stages  of  development.  The  condition  of  society  would  be  materially 
different  were  there  no  gold,  silver,  platinum,  copper,  iron,  tin,  zinc, 
lead,  paladium,  chromium,  aluminium,  manganese,  magnesium,  mer- 
cury, antimony,  or  bismuth. 

Some  minerals  form  foods  without  which  it  would  be  well-nigh 
impossible  for  men  to  exist.  For  example,  salt  and  the  minerals 
which  are  the  source  of  the  alkalies  are  almost  indispensable  to  life. 

The  number  of  minerals  which  are  used  in  the  arts  and  manu- 
factures is  large  and  important.  Sulphur,  phosporus,  soda,  potash, 
chlorine,  fluorine,  and  calcium  contribute  largely  to  the  wealth  of  men. 

Attention  has  already  been  called  to  the  indispensable  character 
of  the  hydrocarbon  compounds.  Without  them  modern  civilization 
would  be  an  impossibility. 

Minerals  as  rock  constituents  form  mountains  and  plains,  and  by 
their  decomposition  furnish  the  ultimate  food  supply  of  mankind. 
The  study  of  minerals  in  their  capacity  of  soil-formers  is  one  of  sur- 
passing interest. 


197 


HISTORY  OF  THE  STUDY  OF  MINERALS 

The  science  of  mineralogy,  depending  as  it  does  upon  physics, 
chemistry,  and  other  well-developed  sciences,  has  been  one  of  the 
latest  to  be  pursued,  although  from  very  early  times  minerals  were 
used  for  ornaments,  weapons,  and  domestic  utensils.  While  ancient 
literature  abounds  in  references  to  minerals,  little  more  was  known 
about  them  in  early  times  than  their  external  form.  Hebrew  litera- 
ture mentions  the  use  of  clay,  niter,  salt,  sand,  and  sulphur,  as  well  as 
of  gold,  silver,  copper,  emerald,  agate,  chalcedony,  carnelian,  jasper, 
onyx,  sardonyx,  topaz,  ruby,  and  sapphire. 

Aristotle,  322  B.C.,  who  is  reputed  by  his  admirers  "to  have 
known  something  of  every  science,"  has  given  no  evidence  of  acquaint- 
ance with  minerals.  Several  references  to  the  subject  in  his  writings 
are  thought  to  have  been  interpolations  made  later  by  other  writers. 
Pliny,  79  A.D.,  was  the  first  Latin  writer  to  describe  minerals,  and  his 
accounts  are  usually  so  incomplete  as  to  leave  doubt  as  to  the  minerals 
to  which  they  apply!  Avicenna  (d.  1036),  an  Arabian  doctor  of 
medicine  born  near  Bokhara,  distinguished  salts,  metals,  minerals, 
and  stones.  Agricola  (d.  1555),  a  German  doctor  born  in  Joachims 
Thai,  used  the  terms  quartz  and  spar,  and  noted  the  hardness,  cleav- 
age, form,  and  luster  of  certain  minerals.  This  is  a  short  list  to 
cover  all  the  years  to  the  seventeenth  century.  But  during  the  latter 
part  of  the  seventeenth  century  a  number  of  men  began  to  be  inter- 
ested in  the  subject,  Robert  Boyle  (1691)  investigating  their  chemis- 
try, Niccolas  Steno  discovering  the  constancy  of  crystal  angles,  and 
Bartholinus  noting  the  double  refraction  of  calcite.  During  the 
eighteenth  century  Linnaeus,  the  great  classifier,  attempted  to 
classify  minerals  according  to  their  form,  while  Cronstedt  attempted 
a  chemical  classification.  Two  Frenchmen,  Rome  de  ITsle  and 
Rene  Just  Haiiy,  were  enthusiastic  investigators  in  crystallography. 
De  ITsle  described  and  pictured  many  forms.  Haiiy  discovered  laws 
underlying  them.  Jealousy  of  each  other's  work  made  them  enemies. 
Haiiy  enjoyed  recording  de  ITsle's  errors  while  correcting  them.  But 
their  work  formed  the  basis  of  later  work  in  crystallography. 

198 


HISTORY  OF  THE  STUDY  OF  MINERALS  199 

During  the  nineteenth  century  the  study  of  minerals  was  pursued 
by  many  workers  and  the  advancement  in  many  lines  assumed 
admirable  proportions.  In  Germany,  Weiss  developed  the  idea  of 
systems  of  crystallization,  Mohs  investigated  the  natural  history  of 
minerals,  and  Werner  studied  chemical  classification  and  developed 
determination  of  minerals  by  simple  physical  characteristics.  In 
Germany,  France,  England,  and  America  the  number  of  workers 
increased,  some  pursuing  the  subject  of  crystal  formation,  as  did 
Bravais,  Sohncke,  Naumann,  Miller,  and  Liebisch;  others  working  at 
the  chemical  side  of  the  subject,  as,  for  example,  Berzelius,  Rose, 
Bunsen,  Mitscherlich,  Plattner,  and  Rammelsberg;  still  others 
studying  optical  mineralogy,  noting  particularly  the  relation  of  form 
to  physical  properties — Brewster,  Senarmont,  Des  Cloizeaux,  Zirkel, 
Sorby,  Wollaston.  The  systematic  side  of  the  subject  was  developed 
by  Beudant,  Breithaupt,  Groth,  and  Dana.  Fouque,  Michel  Levy, 
and  Daubree  gave  attention  to  the  artificial  formation  of  minerals- 

The  increase  in  interest  in  the  subject  of  mineral  study  has  come 
largely  from  advance  in  mining  and  in  the  use  of  minerals  in  arts  and 
manufactures.  The  study  has  been  and  is  naturally  one  of  materials 
rather  than  of  laws;  but  as  the  science  has  progressed,  the  principles 
and  laws  have  been  gradually  perceived  and  formulated.  In  the 
development  of  the  science,  contributions  have  been  made  to  other 
sciences:  to  physics,  knowledge  of  optical  and  electrical  phenomena; 
to  chemistry,  knowledge  of  new  substances;  to  geology,  light  on  the 
origin,  composition,  and  decay  of  rocks;  to  metallography,  facts 
concerning  the  contents  and  treatment  of  ores.  Within  the  last 
fifty  years  the  number  of  workers  in  mineralogy  has  increased  to 
such  an  extent  that  the  list  is  an  extensive  one  and  the  science  has 
been  brought  to  great  perfection  in  various  lines. 

In  the  United  States  many  excellent  books  on  the  subject  have 
been  written.  No  work  has  ever  surpassed  in  completeness  that  of 
James  Dwight  Dana.  His  System  of  Mineralogy,  which  first  appeared 
in  1837,  has  passed  through  six  editions.  After  the  elder  Dana's 
death  the  Manual  of  Mineralogy,  which  first  appeared  in  1848  and 
has  passed  through  thirteen  editions,  and  the  Textbook  of  Mineralogy, 
which  first  appeared  in  1877,  were  rewritten,  enlarged,  and  kept  up 
to  date,  first  by  Edward  Salisbury  Dana  and  later  by  William  E. 
Ford.  Among  many  books  which  have  appeared  during  the  "last 


200  GUIDE  TO  MINERAL  COLLECTIONS 

dozen  years,  the  following  may  be  noted  especially.  In  them  there 
has  been  a  general  endeavor  to  present  this  rather  difficult  science  in 
such  a  manner  as  to  render  it  more  attractive  to  the  general  student. 
Increasing  use  is  made  of  diagrams,  of  models,  and  of  photographs  of 
minerals.  Anyone  wishing  to  pursue  the  subject  further  should  con- 
sult the  following  excellent  works: 

Bayley,  W.  S.,  Descriptive  Mineralogy.    D.  Appleton  &  Co.,  1917. 

Brush,  G.  J.,  and  Penfield,  S.  L.,  Determinative  Mineralogy  and  Blow- 
pipe Analysis.  John  Wiley,  1907. 

Butler,  G.  M.,  Handbook  of  Minerals.    John  Wiley,  1908. 

Erni,  H.,  and  Brown,  A.  P.,  Mineralogy  Simplified.    Philadelphia,  1901. 

Farrington,  0.  C.,  Meteorites.    Lakeside  Press,  1915. 

,  Gems  and  Gem  Minerals.    Lakeside  Press,  1902. 

Fulton,  A.  E.  H.,  Crystallography  and  Practical  Crystal  Measurement. 
Macmillan  Co.,  1911. 

Gratacap,  L.  P.,  Popular  Guide  to  Minerals.  D.  Van  Nostrand  Co., 
1912. 

Groth,  P.,  and  Jackson,  B.  H.,  Optical  Properties  of  Crystals.  John 
Wiley,  1910. 

Iddings,  J.  P.,  Rock  Minerals.    John  Wiley,  1906. 

Johannsen,  Albert,  Determination  of  Rock-Forming  Minerals.  John 
Wiley,  1908. 

Kraus,  E.  H.,  Descriptive  Mineralogy.     George  Wahr,  1911. 

Kunz,  G.  F.,  Gems  and  Precious  Stones  of  North  America.    New  York. 

Lewis,  J.  V.,  Determinative  Mineralogy.    John  Wiley,  1915. 

Merrill,  G.  P.,  Rocks,  Rock  Weathering,  and  Soils.    John  Wiley,  1906. 

,  Non-Metallic  Minerals.    Macmillan  Co.,  1904. 

Moses,  A.  J.,  and  Parsons,  C.  L.,  Mineralogy,  Crystallography,  and 
Blowpipe  Analysis.  D.  Van  Nostrand  Co.,  1909. 

Phillips,  A.  H.,  Mineralogy.    Macmillan  Co.,  1912. 

Pirsson,  L.  V.,  Rocks  and  Rock  Minerals.    John  Wiley,  1908. 

Van  Horn,  F.  R.,  Lecture  Notes  on  Mineralogy.     Cleveland:  1903. 

Winchell,  N.  H.  and  A.  N.,  Elements  of  Optical  Mineralogy.  D.  Van 
Nostrand  Co.,  1909. 

An  attractive  little  monthly  magazine,  The  American  Mineralogist, 
edited  by  Edgar  T.  Wherry,  to  be  obtained  of  H.  W.  Trudell,  Phila- 
delphia, describes  new  minerals  and  records  events  of  interest  to 
mineralogists.  Economic  Geology,  Mineral  Industry,  American  Jour- 
nal of  Science,  Science,  and  other  journals  contain  many  articles  on 
mineralogy.  Various  state  geological  reports  and  those  of  the 
United  States  Geological  Survey  are  full  of  interesting  and  valuable 
information  concerning  occurrence  and  production  of  minerals. 


COMPREHENSIVE  LIST  OF  MINERALS 


2O2 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

I.     ELEMENTS 
i.     Diamond          .... 

c 

Regular 

2.     Bort   

c 

Regular 

3.     Carbonado  

c 

Massive 

4.     Cliftonite  

c 

Massive 

5      Graphite 

c 

Hexag 

6      Schungite 

c 

Amorph 

7.     Sulphur 

s 

Ortho. 

8.     Selensulphur   . 

SeS 

Ortho. 

9.     Arsenic  

As 

Hexag. 

10.     AUemonite  

SbAs3 

Hexag. 

1  1  .     Tellurium  

Te 

Hexag. 

1  2  .     Antimony  

Sb 

Hexag. 

13.     Bismuth 

Bi 

Hexag. 

14.     Zinc 

Zn 

Hexag. 

15.     Gold 

Au 

Regular 

16.     Electrum  

Au«  Ag 

Regular 

17.     Silver  

Ag 

Regular 

18.     Copper  
19.     Mercury  

~° 
Cu 

Hg 

Regular 
Amorph. 

20.    Lead 

Pb 

Regular 

2  1  .    Amalgam 

(Ag,Hg) 

Regular 

22.     Arquerite 

(AgI2Hg) 

Regular 

23.     Kongsbergite     

(Ag,2Hg) 

Regular 

24.     Tin  

Sn 

Tetrag. 

25.     Platinum  

Pt 

Regular 

26.     Iridium  

Ir 

Regular 

27.     Iridosmine 

IrOs 

Hexag. 

28.     Nevyanskite  
29.     Siserskite  
30.    Palladium  

IrOs 
IrOs 
Pd 

Hexag. 
Hexag. 
Regular 

31.    Allopalladium   

Pd 

Hexag. 

3  2  .     Iron  

Fe 

Regular 

33.     Awaruite  

FeNi2 

Regular 

34.    Josephinite  

Fe2Nis 

Regular 

35.     Meteoric  Iron  
36.     Kamacite 

Fe 

Fei4Ni 

Regular 
Regular 

37.     Taenite  

FCnNIn 

Regular 

38.    Plessite  

FenNin 

Regular 

39.     Cohenite  

(Fe,Ni,Co)3C 

Regular 

390.  Schreibersite 

(Fe,Ni,Co),P 

Tetrag. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


203 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

I. 

Colorless 

IO 

3-5 

Kimberley 

Gem 

2. 

3- 

Dark 
Black 

IO 
IO 

3-5 
3-5 

Kimberley 
Kimberley 

}Drills 

4- 

Black 

2-5 

2.  I 

Meteorites 

Carbon 

•     5- 

Black 

I 

2 

Ceylon 

Pencils 

6. 

Black 

I 

1.9 

Russia 

Carbon 

7- 

Yellow 

2 

2 

Sicily 

Drugs 

8. 

Reddish 

Sicily 

Selenium 

9- 

Tin  white 

3-5 

5-6 

Freiberg 

1 

10. 

Tin  white 

3-5 

6.2 

Andreasberg 

fDrugs 

ii. 

Tin  white 

2 

6.1 

Colorado 

J 

12. 
13- 

White 
Reddish 

3 

2-5 

6.6 
9.8 

Japan 
Western  U.S. 

JAlloys 

14. 

White 

2 

6.9 

Australia 

Zinc 

15- 

Yellow 

2-5 

T9 

Western  U.S. 

Coin 

16. 

Amber 

2-5 

15 

Urals 

Gold 

17- 

White 

2-5 

II 

Western  U.S. 

Coin 

18. 

Red 

2.5 

8.9 

Michigan 

Wire 

19. 

White 

17.  C 

California 

Amalgamation 

20. 

Gray 

i-5 

O     3 

"•3 

Colorado 

Lead 

21. 

Whit2 

3 

14 

Sweden,  S.  America 

) 

22. 

White 

3 

TO 

Sweden,  S.  America 

Silver 

23- 

White 

3 

14 

Sweden,  S.  America 

J 

24. 

White 

2 

7 

Siberia,  N.S.  Wales 

Tin 

25- 

White 

5 

21 

Urals 

Dentistry 

26. 

Regular 

6 

22 

Urals 

Pen  points 

27. 

White 

6 

21 

Urals,  S.  America 

28. 

White 

6 

J9 

Urals,  S.  America 

[irdium  and 

2Q. 

White 

6 

21 

Urals,  S.  America 

J     osmium 

30. 

•  31' 

Steel  gray 
Steel  gray 

4 

II 

Brazil 
Hartz 

JPalladium 

32. 

Iron  black 

4 

7 

Meteorites 

33- 

Gray 

5 

8 

New  Zealand 

34- 

Gray 

5 

8 

Oregon 

35- 

Gray 

4 

7 

Meteorites 

36. 

Gray 

4 

7 

Meteorites 

Iron  and  nickel 

37- 

Gray 

4 

7 

Meteorites 

38. 

Gray 

4 

7 

Meteorites 

39- 

Tin  white 

6 

7 

Meteorites 

390. 

Tin  white 

6 

7 

Meteorites 

t 

2O4 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

II.    SULPHIDES 
i.     Sulphides  of  Semi-Metals 
40.     Realgar  

AsS 

Mono 

41.     Orpiment  
42.     Stibnite  

As2S3 
Sb2S3 

Mono. 
Ortho 

43.     Metastibnite 

Sb2S3 

44.     Bismuthinite  
45.     Guana  juatite  .... 

Bi2S3 
Bi2Se3 

Ortho. 
Ortho 

46.    Tetradymite  

Bia(Te,S), 

Hexasr 

47.    Joseite  

Bi,Te,Se 

Hexasr 

48.    Wehrlite  

Bi3Te2 

Hexas 

49.     Molybdenite 

MoS2 

Hexacr 

2.  Sulphides  of  Metals 
a.  Basic 
50.     Dyscrasite  

Ag3Sb-Ag6Sb 

Ortho 

51.     Horsiordite  
52.     Huntilite 

CucSb 
AgiAs 

Ortho. 
Ortho 

53.     Animikite  
54.     Domeykite  

Ag9Sb 
Cu3As 

Ortho. 
Ortho 

55.     Algodonite  

CueAs 

Ortho 

56.     Whitneyite  

CiipAs 

Ortho 

57.     Chilenite 

AgfiBi 

Amorph 

58.     Stiitzite 

AedTe 

Hexag 

b.  Monosulphides 
59.     Galena  . 

PbS 

Ref^ular 

60.     Cuproplumbite  
61.    Alisonite  
62.     Altaite.  .  .  

Cu2S-2PbS 
3Cu2S-PbS 
AgTe 

Massive 
Massive 
Regular 

63.     Clausthalite  

PbSe 

Regular 

64.     Tilkerodite  
65.     Naumannite 

(PbCo)Se 
(Ag2Pb)Se 

Regular 
Regular 

66.     Argentite  

Ag2S 

Regular 

67.    Jalpaite  

(Ag,Cu)2S 

Regular 

68.    Hessite  
69.    Petzite 

Ag2Te 
(Ag  Au)2Te 

Regular 
JMassive 

70.     Aguilarite 

Ag2S  •  Ag2Se 

Regular 

71.     Berzelianite 

Cu2Se 

Dend. 

72.    Lehrbachite  

PbSe-HgSe 

Massive 

73.     Eucairite  

Cu2Se  •  Ag2Se 

Regular 

74.     Zorgite  

(PbCu2Ag2)Se 

Massive 

75.     Crookesite  . 
76.     Umangite  

(CuTlAg)2Se 
CuSe  •  Cu2Se 

Massive 
Massive 

77.     Chalcocite  
78.     Stromeyerite  

Cu2S 
(Ag,Cu)2S 

Ortho. 
Ortho. 

79.     Sternbergite  
80.     Frieseite   

AgFe2S3 
Ag2FesSs 

Ortho. 
Ortho. 

81.     Acanthite  

Ag2S 

Ortho. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


205 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

40. 
41. 

Aurora  red 
Yellow 

1-5 
1-5 

3-5 
3-5 

California 
Utah,  Wyoming 

JArsenic 

42. 

A  -2 

Lead  gray 
Brick  red 

2 

5 

Japan 
Nevada 

JAntimony 

*w» 

44. 

White,  iridescent 

2 

6 

England,  N.C. 

45- 

Bluish  gray 

2 

6 

Mexico 

46. 

Steel  gray 

i-5 

7 

North  Carolina 

Bismuth 

47- 

Steel  gray 

2 

7-9 

Brazil 

48. 

Steel  gray 

•    2 

8-4 

Hungary 

49- 

Lead  gray 

1-5 

4-6 

Washington 

Molybdenum 

5°- 

Tin  white 

3-5 

9-5 

Hartz  Mts. 

Silver 

C  I 

Tin  white 

8.8 

Mytilene 

Copper 

0  A< 

c;2 

Tin  white 

7 

Lake  Superior 

r^r^ 

Ic-M 

0 

C-2 

White 

/ 

Q 

Lake  Superior 

|  Silver 

JO 

CA. 

Tin  white 

V 

7    e 

Lake  Superior 

1 

0*r 

cc. 

Tin  white 

/     0 

7  6 

Lake  Superior 

[•Copper 

00 

<6. 

Reddish  white 

/   *  w 

8-4 

Houghton,  Mich. 

r^r^ 

0 

57- 

Silver  white 

2 

Chile 

^ol\rp>r 

58. 

Lead  gray 

Nagyag 

i  onver 

59- 

Lead  gray 

2-5 

7 

Missouri,  Colorado 

Lead 

60. 

Dark  blue 

6 

Chile 

in 

61. 

Indigo  blue 

6 

Chile 

r  Copper 

62. 

Tin  white 

3* 

8.1 

Chile,  Colorado 

Lead 

63- 

Lead  gray 

3 

8 

Hartz  Mts. 

IT  wr\ 

64. 

Lead  gray 

8 

Hartz  Mts. 

rj_/eau 

65- 

Iron  black 

2-5 

8 

Hartz  Mts. 

66. 
67. 

Lead  gray 
Lead  gray 

2-5 

7 
6 

Western  U.S. 
Mexico 

Silver 

68. 

Lead  gray 

2-5 

8 

Boulder,  Colo. 

'*. 

69. 

Iron  black 

2-5 

9 

California 

Gold 

70. 

Iron  black 

2-5 

7-5 

Mexico 

Silver 

71- 

Silver  white 

2 

6-7 

Sweden 

Copper 

72. 

Iron  black 

7-8 

Hartz  Mts. 

Mercury 

73. 

Lead  gray 

7  •  ^ 

Chile 

Is* 

74- 

Lead  gray 

2 

/    o 

7 

Hartz  Mts. 

^Copper 

75- 

Lead  gray 

3 

6.9 

Sweden 

Silver 

76. 

Cherry  red 

3 

5-6 

Argentina 

Copper 

77- 

Lead  gray 

2 

5 

Montana 

Copper 

78. 

Steel  gray 

2-5 

6 

Siberia,  Colorado 

79- 
80. 

Pinchbeck  .brown 
Dark  gray 

I 
2-5 

4-2 

4 

Saxony 
Joachimsthal 

Silver 

It, 

Iron  black 

2-5 

7 

Joachimsthal 

206 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

II.     SULPHIDES  —  continued 
82.     Sphalerite  

ZnS 

Regular 

83.    Marmatite  

ZnS-FeS 

Regular 

84.    Przibramite  

ZnS  •  CdS 

Regular 

85.    Metacinnabarite 

HgS 

86.     Guadalcazarite  
87.    Tiemannite  

HgS-  ZnS 
HgSe 

Regular 
Regular 

88.     Onofrite  

Hg(S-Se) 

Regular 

89.     Colorado!  te  

HgTe 

Regular 

90.     Alabandite 

MnS 

9  1  .     Oldhamite 

CaS 

Regular 

92.    Pentlandite   

(Fe,Ni)S 

Regular 

93.    Troilite  

FeS 

Hexasr 

94.     Cinnabar  

HgS 

Hexag 

95.     Covellite  

CuS 

Hexag 

96.    Greenockite  

CdS 

Hexag 

97.    Wurtzite 

ZnS 

Hexaer 

98.    Erythrozincite 

ZnS-  MnS 

99.    Millerite  

NiS 

Hexasr 

TOO.    Beyrichite  

NiS* 

Hexag 

101.     Hauchecornite  

(Ni,Co)7(S  Sb  Bi)8 

Tetrag 

102.     Niccolite  

NiAs 

Hexag 

103.     Breithauptite 

NiSb 

Hexacr 

104.     Pyrrhotite 

FcuSiz 

Hexasr 

c.  Intermediate 
105.    Horbachite  

4Fe2S3Ni2S3 

Hexag 

106.     Polydymite  

Ni4Ss 

Regular 

107.     Griinauite  

Ni4Ss-Bi2S3 

Regular 

108.     Sychnodymite  

(Co,Cu)4S5 

Regular 

109.    Melonite  

Ni2Te3 

Hexag. 

no.     Bornite  (  =  Erubesite) 
in.    Linnaeite   . 

3Cu2S-Fe2S3 
(Ni  Co  Fe)3S4 

Regular 
Regular 

112.    Daubreelite  
113.     Cubanite.  

FeS-Cr2S3 
CuFe2S4 

Regular 

1  14.     Carrollite  

CuCo2S4 

Regular 

115.     Chalcopyrite 

CuFeS2 

Regular 

d.  Bisulphides 
116.    Pyrite  

FeS2 

Regular 

117.    Hauerite  

MnS2 

Regular 

1  1  8  .     Smaltite-chloanthite 
119.     Cobaltite  

CoAs2-NiAs2 
CoAsS 

Regular 
Regular 

1  20.     Gersdorffite 

NiAsS 

Regular 

i2i.     Corynite     ...    . 

Ni(As,Sb)S 

Regular 

122.    Willyamite  

CoS2  •  NiS2  •  CoSb2  •  NiSb2 

Regular 

123.     Ullmannite  

NiSbS 

Regular 

124.     Kallilite 

Ni(Sb  Bi)S 

Massive 

125.     Sperrylite 

PtAs2 

Regular 

126.    Laurite 

RuS2 

Regular 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


207 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

82. 

Yellow 

3-5 

3-9 

Missouri 

| 

83. 

Dark  brown 

•2  .Q 

Cornwall 

\Zinc 

O 

84. 

Dark  brown 

3-5 

O    V 

3-9 

Hungary 

1 

85- 

Grayish  black 

3 

7 

California 

86. 

2 

7 

Gaudalcazar.  ]VIex. 

87. 

Steel  gray 

2-5 

/ 

8 

Hartz  Mts. 

Mercury 

88. 

Blackish  gray 

2-5 

8 

Mexico 

89. 

Iron  black 

3 

8 

Colorado 

90. 

Iron  black 

3-5 

3-9 

Colorado 

Manganese 

91. 

Pale  brown 

4 

2-5 

S.C.  Meteorites 

Calcium 

92. 

Bronze  yellow 

3-5 

4.6 

Norway 

Nickel 

93- 

Tombac  brown 

4-7 

4-7 

Meteorites 

Iron 

94. 

Reddish  brown 

2 

8 

Spain,  California 

Mercury 

95- 

Indigo  blue 

i-5 

4-5 

Chile 

Copper 

96. 

Yellow 

3-5 

4-9 

Scotland 

Cadmium 

97- 

Brownish  black 

3-5 

3-9 

Peru 

\7irtr> 

98. 

Red 

2 

3-9 

Siberia 

r£iI!C 

99. 

Brass  yellow 

3-5 

5 

Saxony 

IOO. 

Lead  gray 

3 

4-7 

Westerwald 

IOI. 

Bronze  yellow 

5 

6 

Westphalia 

Nickel 

IO2. 

Copper  red 

5 

7 

Sweden 

103. 

Red 

5 

7-5 

Andreasberg 

104. 

Bronze 

3-5 

4-5 

Pennsylvania 

Sulphur 

105. 

Steel  gray 

4-5 

4 

Horback 

V 

106. 

Gray 

4-5 

4-5 

Griinau 

j^Nickel 

107. 

Steel  gray 

4-5 

5 

Griinau 

I 

108. 

Steel  gray 

4.7 

Siegen 

Cobalt 

109. 

Reddish  white 

T^  •   / 

California 

Nickel 

no. 
III. 

Copper 
Steel  gray 

3 

5-5 

is 

Chile 
Sweden 

Cobalt 

112. 

Black 

5~ 

IVteteoric  iron 

Chromium 

113- 
114- 

Bronze 
Steel  gray 

4 
5-5 

4 
4-8 

Cuba 
Maryland 

r  Copper 

US- 

Yellow 

3-5 

4 

Western  U.S. 

Copper 

116. 

Yellow 

6 

5 

Everywhere 

Sulphur 

117. 

Brown 

4 

3 

Hungary 

Manganese 

118. 
119. 

Tin  white 
Silver  white 

5-5 
5-5 

6 
6 

Saxony 
Sweden 

JGobalt 

120. 
121. 

Silver  white 
Silver  white 

5-5 
4-5 

6 
5-9 

Sweden 
Olsa 

}Nickel 

122. 

Silver  white 

5 

7 

New  South  Wales 

Cobalt 

123. 
124. 

Steel  gray 
Bluish  gray 

5-5 

6 

Germany 
Germany 

JNickel 

125. 

Tin  white 

6 

10 

Canada 

Platinum 

126. 

Iron  black 

7-5 

6-9 

Borneo 

Ruthenium 

208 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

II.     SULPHIDES  —  continued 
127.     Skutterudite  

CoAs3 

Regular 

1  28.     Nickel-skutterudite.  .  . 
129.     Bismuto-smaltite  

(Ni,Co,Fe)As3 
Co(As,Bi)3 

Massive 
Massive 

130.     Marcasite 

FeS2 

Ortho 

131.    Lollingite 

FeAs2 

Ortho. 

132.    Leucopyrite  

Fe3As4 

Ortho. 

133.     Geyerite  

Fe(AsS)2 

Ortho. 

134.     Arsenopyrite  

FeAsS 

Ortho. 

135.     Danaite  

FeCoAsS 

Ortho. 

136.     Saffiorite 

CoAs2 

Ortho. 

137.     Rammelsbergite  
138.     Glaucodot          

NiAs2 
(Co,Fe)AsS 

Ortho. 
Ortho. 

139.    Alloclasite   

Co(As,Bi)S 

Ortho. 

140.    Wolfachite  
1400    M^aucherite 

Ni(As-Sb)S 

Ni3As2 

Ortho. 
Tetrag. 

e.  Tellurides 
141.     Sylvanite 

(Au  Ag)Te2 

Mono. 

142.     Krennerite 

(Au,Ag)Te2 

Ortho. 

143.     Calaverite 

(Au,Ag)Te2 

Mono. 

144.    Nagyagite     

Au2Pbi4Sb3(S,Te)24 

Ortho. 

/.  Oxysulphides 
145.    Kermesite  

Sb2S2O 

Mono. 

146.    Voltzite  

ZnsS4O 

Globules 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


209 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

127. 

Tin  white 

6 

6-7 

Norway 

) 

128. 

Gray 

New  Mexico 

[Cobalt 

I2O 

Tin  white 

6    Q 

Zschorlau 

»*y« 

130. 

Yellow 

6-5 

W  .  VJ 

4-8 

Bohemia 

Sulphur 

I3I- 

Silver  white 

5-5 

7 

Lolling-Huttenberg 

Arsenic 

132. 

Silver  white 

5-5 

7 

Lolling-Huttenberg 

I 

122. 

6.8 

Saxony 

[•Arsenic 

oo 

134- 

Silver  white 

5-5 

6 

Freiberg 

135- 
136. 

Gray 
Tin  white 

5-5 
4-5 

6 

7 

Franconia 
Saxony 

}Cobalt 

137- 

Tin  white 

5-5 

7 

Saxony 

Nickel 

138. 

J39- 

Tin  white 
Steel  gray 

5 
4-5 

5-9 
6.6 

Chile 
Orawitza 

JCobalt 

140. 
1405- 

Silver  white 
Reddish 

4-5 

5 

6 

7 

Wolfach 
Thuringen 

}Nickel 

141. 

Steel  gray 

i-5 

7-9 

Nagyag 

| 

142. 
143- 

Silver  white 
Yellow 

2-5 

8 
9 

Nagyag,  Colo. 
California,  Colo. 

Gold 

144. 

Lead  gray 

i 

6.S 

Nagyag 

J 

145- 

Red 

i 

4-5 

Hungary 

Antimony 

146. 

Red 

4 

3-6 

Joachimsthal 

Zinc 

2IO 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

III.      SULPHO-SALTS 

i.  Sulpharsenites,  etc. 
a.  Acidic 
147.    Livingstonite  

HgS-2Sb2S3 

Ortho 

148.     Chiviatite  

2PbS  '3BiaS3 

Ortho 

149.     Cuprobismutite  

3Cu2S'4Bi2S3 

Ortho 

150.     Rezbanyite 

4PbS'5Bi2S3 

Ortho 

b.  Meta 
151.     Zinkenite   

PbSb2S4 

Ortho 

152.    Andorite  ) 
T53'    Webneritel-  

2(Pb,Ag,Sb),S6 

Ortho 

154.     Sundtite    J 
155.     Sartorite 

PbS-As2S3 

Ortho 

156.     Emplectite 

Cu2S  •  Bi2S3 

Ortho 

157.     Chalcostibite 

Cu2S  •  Sb2S3 

Ortho 

158.     Galenobismutite 

PbS-Bi2S3 

Ortho 

159.     Berthierite  

FeS-Sb2S3 

Ortho 

160.     Matildite  

Ag2S  •  Bi2S3 

Ortho 

161.    Miargyrite  

Ag2S-Sb2S3 

Mono. 

162.    Lorandite  

TlAsS2 

Mono. 

c.  Intermediate 
163.    Plagionite 

5PbS-4Sb2S3 

Miono 

164.    Schirmerite 

3(Ag2,Pb)S-2Bi2S3 

Ortho 

165.     Klaprotholite  . 

3Cu2S'2Bi2S3 

Ortho 

166.     Binnite  

3Cu2S-2As2S3 

Regular 

167.    Warrenite  

3PbS-2Sb2S3 

Ortho. 

168.    Jamesonite  

Pb2Sb2Ss 

Ortho. 

169.     Dufrenoysite  

2PbS-AS2S3 

Ortho. 

1  70.     Rathite 

2PbS-As2S3 

Ortho. 

171.     Cosalite 

2PbS-Bi2S3 

Ortho. 

172.     Kobellite 

2PbS-(Bi,Sb)2S3 

Ortho.    ' 

173.     Brongniardite   .    . 

PbS-Ag2S-Sb2S3 

Regular 

1  74.     Semseyite  

7PbS-3SbaS3 

Mono. 

175.     Schapbachite  

PbS-Ag2S-Bi2S3 

Ortho. 

176.     Freieslebenite  

(Pb,Ag2)s-Sb4Su 

Mono. 

177.    Diaphorite  

(Pb,Ag2)s-Sb4Sn 

Ortho. 

1  80.     Boulangerite 

Pb3Sb2S6 

Ortho. 

181.     Embrithite  

ioPbS'3Sb2S3 

Ortho. 

d.  Ortho 
182.     Bournonite  

(Pb,Cu2)3Sb2Se 

Ortho. 

183.    Aikinite 

3(Pb  Cu2)S-Bi2S3 

Ortho. 

184.    Wittichenite 

3Cu2S-Bi2S3 

Ortho. 

185.     Stylo  typite  .   . 

3(Cu2,Ag2,Fe)S-SbaS3 

Ortho. 

186.    Lillianite  

3PbS-BiSbS3 

Ortho. 

187.    Guitermanite  

3PbS-As2S3 

Ortho. 

188.    Tapalpite  

3Ag2(S,Te)-Bi2(S,Te)3 

Ortho. 

189.    Pyrargyrite 

Ag,SbS, 

Hexag. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


211 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

147. 

Lead  gray 

2 

4-8 

Mexico 

Mercury 

148. 

Lead  gray 

6.9 

Chiviato 

Lead 

140. 

Bluish  black 

6 

Colorado 

Copper 

•Liry  * 
150. 

Lead  gray 

2-5 

6 

Hungary 

^Y 
Lead 

ISI. 

Steel  gray 

3 

5 

Hartz 

Lead 

152. 

| 

153- 

[Dark  gray 

3 

5 

Felsobanya 

Silver 

154- 

J 

ISS- 

Dark  gray 

3 

5 

Binnenthal 

156. 

Tin  white 

2 

6 

Saxony 

Tp,ad 

I57- 

Gray 

3 

4-75 

Hartz 

•LrfCcLU. 

158. 

Lead  gray 

3 

6-9 

Sweden 

159. 

Steel  gray 

2 

4 

Saxony 

Antimony 

1  60. 
161. 

Gray 
Iron  black 

2 

2 

6.9 
5 

Peru 
Saxony 

jSilver        . 

162. 

Red 

2 

5 

Allchar 

Thalium 

163. 

Lead  gray 

2-5 

5 

Wolfsberg 

Lead 

164. 

Lead  gray 

2 

6 

Colorado 

Silver 

165. 
166. 
167. 

Steel  gray 
Steel  gray 
Grayish  black 

2 
2-5 

4-6 
4 

Wittichen 
Tyrol 
Colorado 

}Copper 

J.  \J  /   • 

168. 

Steel  gray 

2 

5-5 

Cornwall 

169. 
170. 

Lead  gray 
Lead  gray 

3 

3 

5-5 
5-5 

Tyrol 
Tyrol 

Lead 

171. 

Steel  gray 

2-5 

6 

Mexico 

172. 

Steel  gray 

6 

Sweden,  Colorado 

•*•/•*•• 
173- 

Black 

3-5 

5.9 

Mexico 

SUver 

174. 

Gray 

<?   0 

Hungary 

Lead 

J.   /  Af-* 

J75- 

Lead  gray 

3-5 

0    V 

6 

4.  J.  UU£  dx  jr 

Schapbach 

Bismuth 

176. 
177. 

Steel  gray 
Gray 

2 

2-5 

6 
S-9 

Frieberg 
Bohemia 

}Silver 

180. 
181. 

Lead  gray 
Lead  gray 

2.5 

2-5 

5-7 

2.5 

France 
Nerchinsk 

}Lead 

182. 

Gray 

2.5 

5-7 

Hartz 

Lead 

183. 
184. 

Lead  gray 
Steel  gray 

2 

3 

6 
4-5 

Urals 
Baden 

>Bismuth 

185. 

Iron  black 

3 

4-7 

Chile 

Antimony 

186. 

Steel  gray 

Sweden 

IT       j 

187. 

Bluish  gray 

3 

S.9 

Colorado 

JLead 

188. 

Gray 

3 

7.8 

Mexico 

Bismuth 

189. 

Black 

2.5 

5.7 

Andreasberg 

Silver 

212 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

III.    SULPHO-SALTS  — 
continued 
190.     Proustite   

Ag^AsS* 

Hexag 

191.     Sanguinite  

A           A      «? 

Ag3ASo3 

Hexaer 

192.     Falkenhaynite  

3Cu2S*Sb2S3 

Regular 

193.     Pyrostilpnite  

3Ag2S-Sb2S3 

Mono. 

1  94      Rittingerite 

AgjoAszSeg 

M^ono 

e.  Basic 
195.    Tetrahedrite  
196.     Freibergite.  
197.     Schwatzite  
198.    Tennantite  

CusSb2S7 
Cu8Sb2S7-Ag2S 
Oi8Sb2S7-HgS 
Cu8As2S7 

Regular 
Regular 
Regular 
Regular 

loo.     Tordanite 

4PbS'As2S3 

Mono. 

200.     Menenghinite  

4PbS-Sb2S3 

Ortho. 

201.     Stephanite  

AgsSbS4 

Ortho. 

202.     Geocronite  

5PbS-Sb2S3 

Ortho. 

203.     Beegerite  

6PbS-Bi2S3 

Regular 

204.     Kilbrickenite  

6PbS-Sb2S3 

Massive 

205     Polybasite 

Ag9SbS6 

Mono. 

206.     Pearceite 

9  Ag2S  •  As2S3 

Mono. 

207.     Polyargyrite 

1  2  Ag2S  •  Sb2S3 

Regular 

2.  Sulphar  -senates,  etc. 
208.     Enargite 

Cu3AsS4 

Ortho. 

209.     Clarite  

Cu3AsS4 

Mono. 

210.    Luzonite  

Cu3AsS4 

Massive 

211.     Famatinite  
212.    Xanthoconite  

3Cu2S-Sb2Ss 
3Ag2S-As2Ss 

Ortho. 
Hexag. 

213      Epiboulangerite 

3PbS-Sb2Ss 

Ortho. 

214.     Epigenite 

4Cu2S  •  3FeS  •  As2S5e 

Ortho. 

215.     Stannite 

Cu2FeSnS4 

Regular 

216.     Argyrodite 

AgjjGeSe 

Regular 

217.     Canfieldite  

AggSnS6 

Regular 

218.     Franckeite  

PbsSb2Sn2SI2 

Massive 

219.     Cylindrite  

Pb6Sb2Sn6SM 

Massive 

220.     Sulvanite  

3Cu2S-V2Ss 

Massive 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


213 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

190. 

IQI 

Scarlet 
Red 

2 
2 

5-S 

Freiberg 
Chile 

jSilver 

*y*« 

IQ2. 

Gray  black 

4-8 

Joachims  thai 

) 

Copper 

o.y  £•  • 
193- 
IQ4- 

Red 
Iron  black 

2 
2 

4 
5-6 

Andreasberg 
Chile 

Jt^lr 

jSilver 

195- 

Iron  black 

3 

4 

Hartz 

Copper 

196. 

Steel  gray 

4  8 

Hartz 

Silver  and  copper 

IO7 

Iron  black 

*r  *  *-* 

ir 

Hartz 

!„ 

"ft  • 
198. 

Iron  black 

3 

0 
4 

Freiberg 

jCopper 

199. 
200. 

Lead  gray 
Lead  gray 

3 

2-5 

6 
6 

Tyrol 
Tuscany 

}Lead 

201. 

Iron  black 

2 

6 

Freiberg 

Silver 

2O2. 

Lead  gray 

2-5 

6 

Sweden 

} 

2O3. 

Gray 

6 

Colorado 

Lead 

•"WO 
2O4. 

Lead  gray 

6 

Ireland 

205. 

Iron  black 

2 

6 

Mexico 

) 

2O6. 

Iron  black 

3 

6 

Colorado,  Montana 

Silver 

207. 

Iron  Black 

2.5 

6.9 

Wolfach 

) 

208. 

Black 

3 

4 

Peru 

209. 
210. 

Gray 
Steel  gray 

3-5 
3-5 

4 
4 

Baden 
Luzon 

Copper 

211. 

Gray 

3-5 

4-5 

Argentina 

212. 

Orange  yellow 

2 

5 

Freiberg 

Silver 

21.3. 

Gray 

6 

Altenberg 

Lead 

214. 

Steel  gray 

•2    tr 

Baden 

Copper 

215. 

Steel  gray 

O    0 

4 

4 

South  Dakota 

X_xV^£/V,l. 

Tin 

216. 

217. 

Steel  gray 
Black 

2-5 

6 

5-5 

Freiberg 
Bolivia 

}Silver 

218. 

219. 

Blackish  gray 
Blackish  gray 

2-5 

5-5 
5 

Bolivia 
Bolivia 

}Lead 

220. 

Bronze 

3 

4 

Australia 

Copper 

214 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

IV.    HALOIDS 
i.  Anhydrous 
221.     Calomel  

Hg2Cl3 

Tetrae 

222.     Nantokite  

Cu2Cl2 

Regular 

223.     Marshite  , 

Cu2I2 

Regular 

224.     Halite 

NaCl 

Regular 

225.    Huantajayite 

2oNaCl-AgCl 

Regular 

226.     Sylvite 

KC1 

Regular 

227.     Sal  ammoniac   

NH4C1 

Regular 

228.     Cerargyrite  

AgCl 

Regular 

229.     Embolite  

Ag(Br,Cl) 

Regular 

230.     Bromyrite  

AgBr 

Regular 

231.     lodobromite  •.  .  .  . 

2AgCl-2AgBr-AgI 

Regular 

232.     Miersite 

Ag2I2 

Regular 

233.     Cuproiodargyrite.  .  .  . 
234.     lodyrite 

CuI-Agl 
Agl 

Incrust. 
Hexaer 

235.     Fluorite   

CaF2 

Regular 

2350.  Yttrofluorite  

(Ca3,Y2)F6 

Regular 

236.    Hydrophilite  

CaCl2 

Regular 

237.     Chloromagnosite  
238.     Scacchite  

MgCl2 
MnCl2 

Regular 
Regular 

239.     Chloralluminite  

A1C13-XH2O 

Regular 

240.     Molysite 

FeClj 

Incrust. 

241.     Sellaite       .    . 

MgF2 

Tetrag. 

242.    Lawrencite  

FeCl2 

Hexag. 

243.     Cotunnite  

PbCl2 

Ortho. 

244.     Tysonite  

(Ce,La,Di)F3 

Hexag. 

245.     Cryolite  

Na3AlF6 

Mono. 

246.     Chiolite  

5NaF-3AlF3 

Tetrag. 

247.     Hieratite 

2KF-SiF4 

Regular 

2.  Oxy  chlorides,  etc. 
248.    Atacamite     

Cu2ClH3O3 

Ortho. 

249.     Percylite  

PbCuO2H2Cl2 

Regular 

2490.  Boleite  

PbCuCl2(OH)24AgCl 

Regular 

2496.  Cumengite  

PbCuCl2(OH)24AgCl 

Tetrag. 

250.    Matlockite 

Pb2OCl2 

Tetrag. 

251.     Mendipite 

Pb2O2Cl2 

Ortho. 

252.    Laurionite 

PbClOH 

Ortho. 

253.     Fiedlerite   

PbClOH 

Mono. 

254.     Penfieldite  

Pb3OCl2 

Hexag. 

255.     Daviesite  

Pb-O-Cl 

Ortho. 

256.     Schwartzembergite..  . 
257.     Fluocerite 

Pb(I,ClJ22PbO 
(Ce,La,Di)aOF4 

Hexag. 
Hexag. 

258.     Nocerite     

2(Ca,Mg)Fe-(Ca,Mg)O 

Hexag. 

259.     Daubreeite  

2Bi2O3-BiCl3-3H2O 

Amorph. 

3.  Hydrous 
260.     Carnallite           * 

KMgCl36HaO 

Ortho. 

261.     Douglasite  
262.     Bischofite  

2KCl-FeCl22H3O 
MgCl2-6H2O 

Mono. 
Mono. 

263.     Kremersite  

KC1  •  NH4C12  •  FeCl2  •  H2O 

Regular 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


215 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

221. 
222. 
223 

Gray 
Colorless 
Oil  brown 

I 
2-5 

6 
3-9 

Spain 
Chile 
New  South  Wales 

Medicine 
}Copper 

224. 
22  ^ 

Colorless 
White 

2.5 

2 

2 

Kansas,  Louisiana 
Chile 

}Salt 

226. 
227. 
228. 
229. 
230. 
231. 
272. 

Colorless 
White 
Pearl  gray 
Grayish  green 
Yellow 
Greenish 
Yellow 

2 

I-S 

I 
I 
2 

i-5 

1.9 

i-5 

5-5 

5-8 
5-7 

Stassfurt 
Vesuvius 
Colorado,  Nevada 
Chile 
Mexico 
Nassau 
New  South  Wales 

Potassium 
Medicine 

Silver 

233- 

234. 
235- 

23Si 
236 

Yellow 
Yellow 
Blue 
Yellow 
White 

2 

i-5 
4 
4 

5-6 
5-6 
3 
3 

2    C 

Peru 
New  Mexico 
Illinois 
Norway 
Vesuvius 

Jlodine 

Flux 
Yttrium,  fluorine 
Chlorine 

237 

White 

Vesuvius 

Magnesium 

238 

White 

Vesuvius 

230 

White 

Vesuvius 

^Chlorine 

24.O 

Red 

Vesuvius 

241. 
242. 

Colorless 
Green 

5 

2-9 

Savoy 
Meteorites 

Fluorine 
Iron 

''4.3. 

White 

5 

Vesuvius 

Lead 

244. 

245- 
246. 

24.7 

Wax  yellow 
Colorless 
Snow  white 
Gray 

4-5 

2-5 

3-5 

6 
2-9 

2.8 

Pike's  Peak 
Western  Greenland 
Ilmen  Mts. 
Vulcano 

Cerium 
>Aluminum 
Potassium 

248. 

24.Q. 

Green 
Blue 

3 

2  t; 

3-7 

Arizona 
Mexico 

Copper 

2490. 
2406. 

Indigo  blue 

3 

5 

Lower  California 

Lead  and  copper 

250. 
251. 

2  C2 

Yellowish 
White 
Colorless 

2-5 
2-5 

7 
7 

Cromford 
England 
Greece 

2  C3 

Colorless 

Greece 

Lead 

2  <\A. 

White 

Greece 

2  C  C. 

Colorless 

Sierra  Gorda 

256. 
257- 

2^8. 

Honey  yellow 
Yellow 
White 

2 

4 

6 

5-7 

Atacama 
Sweden 
Italy 

Cerium 
Fluorine 

259- 

260. 
261. 
262. 
263. 

Yellow 

White 
Colorless 
Colorless 
Red 

2 

I 
I 

6 
1.6 

2 

1.6 

Bolivia 

Stassfurt 
Stassfurt 
Prussia 
Vesuvius 

Bismuth 
Magnesium 
ichlorine 

2l6 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

IV.    HALOIDS  —  continued 
264.     Erythrosiderite  

2KCl-FeCl3-H2O 

Ortho. 

265.    Tachhydrite  
266.     Fluellite 

CaCl2-2MgCl2-i2H20 
A1F3-H2O 

Hexag. 
Hexag 

267.    Prosopite  
268.     Pachnolite  

CaF2-2Al(F,OH)3 
NaF-CaF2-AlF3-H2O 

Mono. 
Mono. 

269.    Thomsenelite      .... 

NaCaAlF6-H2O 

Mono. 

270.     Gearksutite  
271.     Ralstonite  

CaF2-Al(F,OH)3-H20 

(Na2Mg)F2  •  3  A1(F,OH)3  •  2H2O 

Earthy 
Regular 

272      Tallingite 

Cus(OH)8Cl2-4H2O 

Botry 

273.     Footeite 

8Cu(OH)2  •  CuCl2  •  4H2O 

Mono. 

274.    Yttrocerite 

(Y  Er,Ce)F3-sCaF6-H2O 

Earthy 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


217 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

264. 

Red 

Vesuvius 

261?. 

Yellow 

Stassfurt 

|  Chlorine 

266. 

Colorless 

3 

2 

Cornwall 

267. 

Colorless 

4-5 

2.8 

Colorado 

268. 

Colorless 

3 

2.9 

Colorado 

Fluorine 

269. 

Colorless 

2 

2.9 

Colorado 

270. 

White 

2 

Colorado 

271. 

Colorless 

4-5 

2-5 

Greenland 

272. 
273. 

Blue 
Blue 

3 

3-5 

Cornwall 
Arizona 

J  Copper 

274. 

Blue 

4 

3 

Sweden 

Yttrium 

218 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

V.    OXIDES 
i.  Oxides  of  Silicon 
27  <.    Ouartz 

SiO2 

Hexag 

276.     Star  quartz  

SiO2 

Hexag 

277.    Amethyst  

SiO2 

Hexag 

278.    Rose  quartz  
2  79      Citrine 

Si02 
SiO2 

Hexag. 
Hcxa<y 

280.     Cairngorm  
281.     Milky  quartz     .... 

Si02 
SiO2 

Hexag. 
Hexag 

282.     Sapphire  quartz.  .  .  . 

SiO2 

Hexag 

283.     Sagenitic  

SiO2 

Hexag. 

284.    Cat's  eye  

SiO2 

Hexag. 

285.    Aventurine  

SiO2 

Hexag. 

286.     Chalcedony  
287.     Carnelian 

Si02 
SiO2 

Crypto. 
Crypto 

288.     Chrysoprase  

SiO2 

Crvoto 

289.    Prase  

SiO2 

Crypto. 

290.    Plasma  

SiO2 

Crypto. 

291.    Agate  

SiO2 

Crypto. 

292.    Onyx  

SiO2 

Crypto. 

293.    Sardonyx 

SiO2 

Crypto 

294.     Siliceous  sinter     .  .  . 

SiO2 

Crypto. 

20  c.     Flint 

SiO2 

Crypto. 

296.     Hornstone  

SiO2 

Crypto. 

297.    Basanite  

SiO2 

Crypto. 

298.    Jasper.  .  . 

SiO2 

Crypto. 

2  99      Quartzite 

SiO2 

Crypto. 

300.    Itacolunite 

SiO2 

Crypto. 

301.    Buhrstone   

SiO2 

Crypto. 

302.     Silicified  wood  

SiO2 

Crypto. 

303.     Quartzine  

SiO2 

Triclinic 

304.    Tridymite  

SiO2  • 

Hexag. 

305.     Asmanite  

SiO2 

Ortho. 

306      Cristobalite 

SiO2 

Regular 

307     Melanophlogite 

SiO2-Oj 

Regular 

308      Opal       

SiO2-H2O 

Amorph  . 

309.     Precious  opal  

SiO2-H2O 

Amorph. 

310.    Fire  opal  

SiCVHaO 

Amorph. 

311      Girasol 

SiO2-H2O 

Amorph. 

312      Resin  opal 

SiO2-H2O                                        t 

Amorph. 

•7  T  7      HvdroDhane 

SiO2-HaO 

Amorph. 

314     Milk  opal         

SiO2-H2O 

Amorph. 

315.     Cacholong  

SiO2-HaO 

Amorph. 

316.    Opal  agate  

SiO2-H2O 

Amorph. 

317     M  enilite 

SiO2-HaO 

Amorph. 

318     Wood  opal 

SiO2-H2O 

Amorph. 

319     Hyalite         

SiO2-H2O 

Amorph. 

320.    Pearl  sinter  

SiO2-H2O 

Amorph. 

SKVHaO 

Amorph. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


219 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

275- 

Colorless 

7 

2.6 

Ubiquitous 

Abrasives 

276. 

Whitish 

7 

2.6 

South  America 

277. 

Purple 

7 

2.6 

Colorado 

278. 

Pink 

7 

2.6 

Black  Hills 

279. 

Yellow 

7 

2.6 

Colorado 

280. 
281. 

Brown 
Milk  white 

7 
7 

2.6 
2.6 

Scotland 
Alleghanies 

Ornaments 

282. 

Indigo 

7 

2.6 

Brazil 

283. 

Colorless 

7 

2.6 

Brazil 

284. 

Milky 

7 

2.6 

Ceylon 

285. 

Red 

7 

2.6 

Colorado 

286. 
287. 

Various 
Red. 

7 
7 

2.6 
2.6 

Ubiquitous 
Brazil 

Various 
Gems 

288. 

Green 

7 

2.6 

Colorado 

Gems 

289. 

Leek  green 

7 

2.6 

Saxony 

290. 

Green 

7 

2.6 

India 

291. 

Banded 

7 

2.6 

Colorado 

Ornaments 

292. 

Black  and  white 

7 

2.6 

Colorado 

293- 

Banded 

7 

2.6 

Colorado 

294. 

White 

7 

2.6 

Yellowstone  Park 

Rock  forming 

2QS- 

Brown 

7 

2.6 

Chalk  Cliffs 

Arrow  points 

296. 
297- 

Brown 
Black 

7 
7 

2.6 
2.6 

Wyoming 
California 

^Abrasives 

; 

298. 

Red 

7 

2.6 

Colorado      ., 

Ornaments 

299. 

Various 

7 

2.6 

Wisconsin 

Rock  forming 

300. 

Gray 

7 

2.6 

North  Carolina 

Curios 

301. 

Gray 

7 

2.6 

North  Carolina 

Millstones 

302. 

Various 

7 

2.6 

Arizona 

303. 

Various 

7 

2.6 

Colorado 

304. 
30?. 

Colorless 
Colorless 

7 

2 

Yellowstone  Park 
Meteorites 

rnaments 

owo 
306. 

White 

6-5 

2 

Mexico 

307- 

Brown 

6-5 

2 

Sicily 

308. 

Various 

5-5 

1.9 

Hungary 

309. 

Various 

5-5 

1.9 

Hungary 

310. 

Red  to  yellow 

c  .  c 

Mexico 

Gems 

o 
311. 

Bluish  white 

o   o 
c  .  c 

Mexico 

312. 

Yellow 

o   o 
c.  c 

Mexico 

313. 

White 

O     3 

5-5 

•9 

Mountains 

314. 
315. 

Milk  white 
White 

5-5 
5-5 

•9 
•9 

Mountains 
Hungary 

Gems 

316. 

Light 

5-5 

•9 

Mountains 

317. 

Amber 

c.  c 

.0 

France 

318 

Dull  grayish 

J      -J 

c.  c 

y 
.9 

Colorado 

319. 

Colorless 

o     <J 

5-5 

V 

.9 

New  Jersey,  Conn. 

320. 

White 

ir    r 

7 

I    O 

Yellowstone  Park 

321. 

White 

O    0 

C      IT 

•  •  y 

I    O 

Yellowstone  Park 

0    0 

j.  .  y 

220 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

V.     OXIDES  —  continued 
322.     Float  stone  

SiO2-H2O 

Amorph. 

323.     Tripolite  

SiO2-H2O 

Amorph. 

324.    Infusorial  earth  

SiO2-H2O 

Amorph. 

2.  Semi-Metals 
325.     Arsenolite  

As2O3 

Regular 

326      Claudetite 

As2O3 

Mono. 

327      Senarmontite 

SbA 

Regular 

328.     Valentinite 

Sb2O3 

Ortho. 

329.     Bismite       .... 

BiA 

Ortho. 

330.     Tellurite  

TeO2 

Ortho. 

331.     Molybdite  

MoO3 

Ortho. 

332.     Tungstite  

WO3 

Ortho. 

333.     Cervantite  

SbA'  SbA 

Ortho. 

334.     Stibiconite  

H2Sb2Os 

Massive 

3.  Metals 
a.  Protoxides 
335.     Cuprite....  
336.     Chalcotrichite  
•777      Tile  ore 

Cu2O 
Cu2O 
Cu2O 

Hexag. 
Hexag. 
Hexag. 

338      Ice 

H2O 

Hexag. 

JJV.           AV,V.    

339      Penclase 

MgO 

Regular 

340.     Manganosite  
341      Bunsenite  

MnO 
NiO 

Regular 
Regular 

342.     Zincite  :  .  .  .  . 

ZnO 

Hexag. 

343.     Massicot  

PbO 

Massive 

344.    Tenorite  

CuO 

Mono. 

345.     Paramelaconite  

CuO 

Tetrag. 

b.  Sesquioxides 
346.     Corundum  
347.     Sapphire  
34.8      Rubv 

A1203 
A1203 
A12O3 

Hexag. 
Hexag. 
Hexag. 

340.     Emery 

A12O3 

Hexag. 

350.     Hematite  

Fe2O3 

Hexag. 

351.     Specular  hematite  
352.     Columnar  hematite.  .. 
353.     Red  ocherous  hematite 
354.     Clay  ironstone  
355.     Martite  

Fe203 
FeA 
FeA 
Fe203 
Fe2O3 

Hexag. 
Hexag. 
Hexag. 
Hexag. 
Regular 

356.     Ilmenite  

FeTiO3 

Hexag. 

3^7      PvroDhanite 

MnTiO3 

Hexag. 

c.  Intermediate  Oxides 
358      Spinel                     .... 

MgAlA 

Regular 

359.     Ruby  spinel  
360.     Ceylonite-pleonaste.  .  . 

MgAlA 
(Mg,Fe)O-Al2O3 

Regular 
Regular 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


221 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

•j  22 

White 

e    er 

I    0 

Yellowstone  Park 

o^-6' 
323. 
324. 

White 
Gray 

0  •  0 

5-5 
5-5 

•  V 

I.Q 
1.9 

Virginia 
Missouri 

>Abrasives 

32^. 

Colorless 

3-7 

California 

Drugs 

O     3 
326. 

White 

2-5 

3-8 

Portugal 

Arsenic 

327- 
328. 

White 
White 

2 
2-5 

5-3 
5 

Quebec 
New  Brunswick 

^Antimony 

-22Q, 

Straw  yellow 

4   -2 

Cornwall 

Bismuth 

O     V* 

330- 

White 

2 

^    O 

5-9 

Boulder,  Colo. 

Tellurium 

331- 

Straw  yellow 

I 

4-5 

Pennsylvania 

Molybdenum 

332. 

Yellow 

North  Carolina 

Tungsten 

OO     * 

333- 
334- 

Yellow 
Yellow 

4 
4 

4 
5 

Spain 
Arkansas 

>Antimony 

335- 

Red 

3-5 

5-8 

W.  United  States 

1 

336. 

Red 

3-5 

5-8 

Arizona 

Copper 

337- 

Brown 

3-5 

5-8 

Arizona 

J 

338. 

Colorless 

i 

o.-9 

Cold  regions 

Ice 

339- 

Grayish 

6 

3-6 

Sweden 

Magnesium 

340. 

Green 

5 

5 

Sweden 

Manganese 

34i. 

Green 

5 

6 

Johanngeorgen- 

stadt 

Nickel 

342. 

Red 

4 

5 

New  Jersey 

Zinc 

343- 

Yellow 

2 

8 

Mexico 

Lead 

344. 
345- 

Black 
Black 

3 

5 

5-8 
5-8 

Tennessee 
Arizona 

>  Copper  . 

346. 

Various 

9 

4 

Appalachians 

Abrasives 

347- 
348. 

Blue 
Red 

9 
9 

4 

4 

Ceylon 
Upper  Burma 

JGems 

349- 

Black 

9 

4 

New  York 

Abrasives 

350- 

Red 

6 

5 

New  York 

351- 

Black 

6 

5 

Elba 

352. 

Brownish  red 

6 

5 

New  York 

Iron 

353- 

Red 

3 

5-4 

Minnesota 

354- 

Brownish  black 

3 

3 

Minnesota 

355- 
356. 

Iron  black 
Iron  black 

6 

5 

4-8 
4-5 

East  U.S. 
East  U.S. 

Jlron 

357- 

Red 

5 

4-5 

Sweden 

Manganese 

358. 

Red 

8 

3-5 

New  York 

) 

359- 

Red 

8 

3-6 

New  York 

^Gems 

360. 

Brown 

8 

3-5 

New  York 

I 

222 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

V.    OXIDES  —  continued 
361.     Chlorospinel  

MgO-(Al,Fe)2O3 

Regular 

362.     Picotite-chrome  spinel 
363.    Hercynite  

(Mg,Fe)0-(Al,Fe,Cr)A 
FeAl2O4 

Regular 
Regular 

3  64      Ga.hn.ite 

ZnAl2O4 

Regular 

365.     Automolite  
366      Dysluite       

ZnAl2O4 
(Zn,Fe,Mn)0  •  (Al,Fe)2O3 

Regular 
Regular 

367      Kreittonite  

(ZnFe,Mg)O(Al,Fe)2O3 

Regular 

368      Miagnetite 

FeO-Fe2O3 

Regular 

360      Franklinite 

(Fe,Zn,Mn)O-  (Fe,Mn)2O3 

Regular 

370.     Magnesioferrite  
371.     Jacobsite  
372      Chromite       

MgFeO4 

(Mn,Mg)0-(Fe,Mn)203 
FeO-Cr2O3 

Regular 
Regular 
Regular 

3  7  •?      Chrvsoberyl  . 

BeAl2O4 

Hexag. 

374      Alexandrite  

BeAl2O4 

Hexag. 

•?7c      Cat's  eve 

BeAl2O4 

Hexag. 

•176      Hausmannite 

Mn3O4 

Tetrag. 

377      JVlinium                

Pb3O4 

Powder. 

378      Crednerite       

Cu3Mn4O9 

Mono. 

379     Pseudobrookite  

Fe4(TiO4)3 

Ortho. 

380     Braunite     

3Mn2O3-MnSiO3 

Tetrag. 

381      Bixbyite  

FeO-MnO2 

Regular 

d.  Dioxides 
382      Cassiterite  

SnO2 

Tetrag. 

383      Stream  tin  

SnO2 

Tetrag. 

384      Polianite                  .  . 

MnO2 

Tetrag. 

385      Rutile               

TiO2 

Tetrag. 

386      Nigrine         

TiO2(+2%Fe2O3) 

Tetrag. 

387      Ilmenorutile  

TiO2(+io%Fe2O3) 

Tetrag. 

388     Plattnerite  

PbO2 

Tetrag. 

380      Baddeleyite 

ZrO2 

Mono. 

390     Octahedrite 

TiO2 

Tetrag. 

•?QJ      Brookite                 .... 

TiO2 

Ortho. 

392      Pyrolusite        

MnO2 

Amorph. 

e.  Hydrous  Oxides 
ao3      DiasDore 

A12O3-H2O 

Ortho. 

394      Goethite  

Fe2O3-H2O 

Ortho. 

•?o<      M^antranite 

Mn2O3-H2O 

Ortho. 

396      Limonite 

2Fe2O3-3H2O 

Amorph. 

3O7      Bo£  ore 

2Fe2O3-3H2O 

Amorph. 

398.     Clay  ironstone  
OQQ      Turgite 

2Fe2O3-3H2O 
2Fe2O3-H2O 

Amorph. 
Amorph. 

400.     Xanthosiderite  
401      Bauxite 

Fe2O3-2H2O 
A12O3  •  2H2O 

Amorph. 
Grains 

402      ^^ocheinite                .  . 

A12O3-2H2O 

Grains 

403      Brucite           

MgO-H2O 

Hexag. 

404      Pyrochroite   

MnO-H2O 

Hexag. 

40  'C      Gibbsite 

A12O3-H2O 

Mono. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


223 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

36l 

Green 

8 

3-5 

New  York 

Gems 

362! 

Brown 

8 

4 

N.Y.  and  N.J. 

363- 

Black 

7-5 

3-9 

Ronsberg 

Iron 

364- 

Green 

7-5 

4 

New  Jersey 

365- 

Green 

7-5 

4 

Sweden 

366. 

Brown 

7-5 

4 

Pennsylvania 

Zinc 

367. 

Black 

7 

4 

Brazil 

368. 

Iron  black 

5-5 

5 

Adirondacks 

Iron 

Black 

6 

5 

New  Jersey 

Zinc 

37°- 

Iron  black 

6 

4-5 

Vesuvius 

Magnesium 

Black 

6 

4-7 

Sweden 

Manganese 

372. 

Black 

5-5 

4-5 

W.  United  States 

Chromium 

373- 

Green 

8-5 

3-5 

Urals 

374- 

Green 

8-5 

3-6 

Urals 

Gems 

375- 

Greenish 

8-5 

3-6 

Ceylon 

376. 

Black 

5 

4.8 

Sweden 

Manganese 

377- 

Red 

2 

4.6 

Baden 

Lead 

378. 

Iron  black 

4-5 

4-9 

Friedrichsrode 

Manganese 

379- 

Dark  brown 

6 

4 

Transylvania 

Titanium 

380. 

Dark  brown 

6 

4-7 

Hartz 

Manganese 

381- 

Black 

6 

4-9 

Utah 

Iron 

382. 

Black 

7 

7 

Malay  Peninsula 

\Tin 

383- 

Black 

7 

7 

Malay  Peninsula 

>  jLin 

384. 

Steel  gray 

6 

4-9 

Bohemia 

Manganese 

385- 

Red 

6-5 

4 

Arkansas 

I 

386. 

Black 

6-5 

4 

Arkansas 

^Titanium 

387. 

Black 

5 

Ilmen  Mts. 

J 

o    / 

388. 

Iron  black 

5-5 

8-5 

Idaho 

Lead 

389. 

Colorless 

6-5 

5-5 

Ceylon 

Zirconium 

39°- 
391- 

Brown 
Brown 

5 
5-5 

3-8 

3-8 

Rhode  Island 
Arkansas 

>Titanium 

392. 

Black 

2 

4-7 

Alabama 

Manganese 

393- 

White 

6-5 

3 

North  Carolina 

Aluminum 

394- 

Brown 

5 

4 

Pa.,  Colorado 

Iron 

395- 

Black 

4 

4 

Colorado 

Manganese 

396, 

Brown 

5-5 

3-8 

Minnesota 

397- 

Brown 

2 

3-8 

Minnesota 

398. 

Brown 

2 

3-8 

Widespread 

Iron 

399- 

Brown 

2 

4-1 

Connecticut 

400. 

Yellow 

2-5 

4-1 

Hartz  Mts. 

401. 

402. 

Gray 
Gray 

3 
3 

2-5 

2-5 

Arkansas 
Carniola 

JAluminum 

403- 

White 

2-5 

2 

New  York 

Magnesium 

404. 

White 

2-5 

3-2 

New  Jersey 

Manganese 

405- 

White 

2.5 

2 

New  York 

Aluminum 

224 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

V.    OXIDES  —  continued 
406.     Sassolite  

B2O3-3H2O 

Triclin 

407.    Hydro  talcite  

Al2O3-6MgO-isH2O 

Hexag. 

468.     Pyroaurite  

FeA-aMgO-isHaO 

Hexag. 

409.     Chalcophanite  

(Mn,Zn)O  •  2MnO2  •  2H2O 

Hexag. 

410.     Psilomelane  
411.    Wad 

H4MnOs 
H4MnOs-H2O 

Massive 
Amorph 

412.     Bog  manganese  

H4MnO5-H2O 

Amorph. 

413.     Asbolite  

H4MnO5-H2O-CoO 

Amorph. 

414     Lampadite 

H4MnOs  •  H2O  •  (Co  •  Cu)  O 

Amorph. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


225 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

406. 
407. 

4.08 

White 
White 
White 

I 
2 

1-4 

2 

California 
Norway 
Sweden 

Boric  acid 
JMagnesium 

409. 
410. 
411. 
412. 

413- 
414. 

Iron  black 
Iron  black 
Black 
Black 
Black 
Black 

2-5 

6 
6 
6 

3-9 
4 
3 
3 
3 

New  Jersey 
Arkansas 
Germany 
Germany 
Germany 
Germany 

Manganese 

226 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 


Form 


VI.    CARBONATES 
i.  Anhydrous 

415.  Calcite 

416.  Dog-tooth  spar 

417.  Nail-head  spar 

418.  Iceland  spar 

419.  Fontainebleau  lime- 

stone  

420.  Satin  spar 

421.  Argentine 

422.  Aphrite 

423.  Saccharoid.  limestone. 

424.  Shell  marble 

425.  Lumachelle 

426.  Ruin  marble 

427.  Lithographic  stone. . . 

428.  Hydraulic  limestone. . 

429.  Chalk 

430.  Oolite 

431.  Pisolite 

432.  Stalactite 

433.  Stalagmite 

434.  Calc  sinter 

435.  Travertine 

436.  Agaric  mineral 

437.  Rock  meal 

438.  Thinolite 

439.  Dolomite 

440.  Magnesite 

441.  Breunnerite 

442.  Mesitite 

443.  Pistomesite 

445.  .  Siderite 

446.  Spherosiderite 

447.  Rhodochrosite 

448.  Smithsonite 

449.  Sphaerocobaltite 

450.  Aragonite 

451.  Flos  fern 

452.  Tarnowitzite .  .  .  '. . . . . 

453.  Witherite 

454.  Bromlite 

455.  Strontianite 

456.  Cerussite 

457.  Barytocalcite 

458.  Bismutospharite 

459.  Parisite 

460.  Bastnasite 

461.  Phosgenite 

462.  Northupite 


CaCO3 
CaC03 
CaC03 
CaC03 

CaC03 

CaC03 

CaC03 

CaC03 

CaC03 

CaC03 

CaCO3 

CaC03 

CaC03 

CaCO3,  also  SiO2,Al2O3,  etc. 

CaC03 

CaC03 

CaCO3 

CaC03 

CaC03 

CaC03 

CaC03 

CaC03 

CaCO3 

CaCO3 

(Ca,Mg)C03 

MgC03 

MgC03-H20 

2MgC03-FeCO3 

MgCO3-FeCO3 

FeCO3 

FeC03 

MnC03 

ZnC03 

CoC03 

CaC03 

CaC03 

CaC03-PbCO3 

BaC03 

(Ba,Ca)CO3 

SrC03 

PbC03 

BaCO3-CaCO3 

Bi2(CO3)3-2Bi2O3 

(CaF)(CeF)Ce(C03)3 


(PbCl)2C03 
MgC03-Na2CO3-NaCl 


Hexag. 
Hexag. 
Hexag. 
Hexag. 

Hexag. 

Hexag. 

Lamellar 

Lamellar 

Crypto. 

Shelly 

Chatoy. 

Brecci. 

Massive 

Massive 

Massive 

Granular 

Grains 

Cylind. 

Cylind. 

Incrust. 

Incrust. 

Grains 

Grains 

Grains 

Hexag. 

Hexag. 

Hexag. 

Hexag. 

Hexag. 

Hexag. 

Concret. 

Hexag. 

Hexag. 

Hexag. 

Ortho. 

Stalact. 

Stalcat. 

Ortho. 

Ortho. 

Ortho. 

Ortho. 

Mono. 

Spherical 

Hexag. 

Hexag. 

Tetrag. 

Regular 


COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


227 


No 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

4I5- 

Colorless 

3 

2-7 

Ubiquitous 

V 

416. 

Colorless 

3 

2-7 

Missouri 

^Calcium 

417. 

Colorless 

3 

2-7 

Missouri 

I 

418. 

Colorless 

3 

2.7 

Iceland 

Prisms 

419. 

Colorless 

3 

2.7 

France 

420. 

Colorless 

3 

2-7 

France 

421. 

White 

3 

2-7 

France 

422. 

White 

3-5 

2.7 

France 

423- 

Yellow 

3 

2-7 

France 

424. 

Yellow 

3 

2-7 

Carinthia 

425. 

Dark  brown 

3 

2-7 

France 

426. 

Brown 

3 

2.7 

Italy 

427. 

Buff' 

3 

2-7 

Solenhofen 

428. 
429. 

Buff 
White 

3 
3 

2-7 
2.7 

Virginia 
England 

Calcium 

430- 

White 

3 

2.7 

Missouri 

431- 

White 

3 

2.7 

Missouri 

432. 

White 

3 

2-7 

Kentucky 

433- 

White 

3 

2-7 

Kentucky 

434- 

White 

3 

2.7 

Yellowstone  Park 

435- 

White 

3 

2-7 

Tivoli 

436. 

White 

3 

2.7 

Caverns 

437- 

White 

3 

2-7 

Paris 

438. 

Yellow 

3 

2-7 

Nevada 

439- 

White 

3-5 

2.8 

Illinois 

Building 

440. 

Colorless 

4 

3 

Greece 

| 

441. 
442. 

White 
Yellowish 

4 
3-5 

3 
3 

Massachusetts 
Traversella 

>Magnesium 

443- 

Yellowish 

3-5 

3 

Traversella 

j 

445- 
446. 

Gray 
Brown 

3-5 
3-5 

3-8 

3-8 

Germany 
E.  United  States 

Jlron 

447- 

Red 

4 

3 

Colorado 

Manganese 

448. 

White 

5 

4 

Pennsylvania 

Zinc 

449. 

Red 

4 

4 

Saxony 

Cobalt 

450. 

Colorless 

3-5 

2.9 

New  York,  Illinois 

451. 

White 

3-5 

2.9 

New  York,  Illinois 

Calcium 

452. 

White 

2  .0 

Silesia 

453- 
454- 

Colorless 
White 

3-5 

4 

V 
4-2 

3-7 

England 
England 

JBarium 

455- 

Colorless 

3-5 

3-7 

New  York 

Strontium 

456: 

Colorless 

3-5 

6 

Cordilleras 

Lead 

457- 

White 

4 

3-6 

Cumberland 

Barium 

458. 

Yellow 

3 

7 

Saxony 

Bismuth 

459- 

Yellow 

4-5 

4 

Colombia 

Cerium 

460. 

Yellow 

4 

4-9 

Colorado 

Lanthanum 

461. 

White 

2.7 

6 

England 

\T  Aorl 

462. 

White 

California 

f-ueau 
1 

228 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

VI.    CARBONATES  —  continued 
2.  Hydrous 
463.     Teschemacherite 

HNH4CO3 

Ortho 

464.     Malachite  

CuCO3-Cu(OH)2 

Mono 

465.     Azurite  

2CuCO3-Cu(OH)2 

Mono 

466.     Chessylite  

2CuCO3-Cu(OH)2 

Mono. 

467.     Aurichalcite  

2(Zn,Cu)CO3*3(Zn,Cu)(OH)2 

Mono. 

468.     Hydrozincite  
469.     Hydrocerussite  
470.     Dawsonite   

ZnC03-2Zn(OH)2 
2PbCO3-Pb(OH)2 

Na3Al(CO3)3  •  2  A1(OH)3 

Earthy 
Hexag. 
Mono 

471.     Thermona  trite  

Na2CO3-H2O 

Ortho. 

472.     Nesquehonite  

MgCO3-3H2O 

Ortho. 

473      Natron 

Na2CO3-ioH2O 

M!ono 

474.     Pirssonite 

CaCO3  •  Na2CO3  •  2H2O 

Ortho 

475.     Gaylussite  
476.    Lanthanite 

CaOVNa2C03-5H20 
La2(CO3)3-9H2O 

Mono. 
Ortho. 

477.     Trona  

Na2CO3  •  HNaCO3  •  2H2O 

Mono. 

478.     Hydromagnesite  
479.    Hydrogioberite  
480.    Lansfordite  

3MgC03-Mg(OH)2-3H20 
MgC03-Mg(OH)2-2H20 
3MgCO3  •  Mg(  OH)2  •  2  iH2O 

Amorph. 
Compact 
Triclin. 

481.    Zaratite 

NiCO3-2Ni(OH)2-4H2O 

Stalact. 

482.     Remingtonite 

CaCO3-H2O 

Incrust. 

483.     Tengerite 

YCO3-H2O 

Pulver. 

484.     Bismutite  

Bi2O3-CO2-H2O 

Amorph. 

485.     Uranothallite  
486.     Liebigite  

2CaCO3-U(CO,)2-ioH2O 
CaCO3  •  (UO2)  CO3  •  2oH2O 

Ortho. 
Concret. 

487.     Voglite 

(UCa  Cu)Co3-H2O 

Scales 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


229 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

463- 

Yellow 

1-5 

1-4 

Africa 

Lead 

464. 

Green 

3-5 

4 

Arizona 

I 

465- 

Blue 

3-5 

3-7 

Arizona 

[Copper 

466. 

Blue 

3-5 

3-7 

France 

J 

467. 

Green 

2 

3-5 

France 

\ 

468, 

White 

2 

3-5 

Pennsylvania 

jZinc 

469. 

Colorless 

2 

6 

Sweden 

Lead 

470. 
471. 

White 
White 

3 

i 

2 

Tuscany 
Nevada 

>Aluminum 

472. 

Colorless 

2-5 

1.8 

Pennsylvania 

Magnesium 

473- 
474- 

Gray 
Colorless 

i 
3-5 

2-3 

Egypt 
California 

(Sodium 

475- 

White 

2-3 

1.9 

Utah 

476- 

White 

2-5 

2.6 

Pennsylvania 

Lanthanum 

477- 

Gray 

2-5 

2 

Nevada 

Sodium 

478. 

White 

3-5 

2 

New  Jersey 

] 

470- 

Gray 

2 

Italy 

[Magnesium 

*T  /  V 

480. 

White 

2-5 

Pennsylvania 

481. 

Green 

3 

2 

Texas 

Nickel 

482. 

Rose 

2 

Maryland 

Cobalt 

483. 

White 

Texas 

Ytterium 

484. 

White 

4 

6.8 

South  Carolina 

Bismuth 

485- 

Green 

2 

Bohemia 

| 

486. 

Green 

2 

Joachims  thai 

[•Uranium 

487. 

Green 

Joachims  thai 

*t?f  /  • 

/ 

230 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

VII.    SILICATES 
i.  Anhydrous 
a.  Disilicates 
488.    Petalite  

LiAl(Si2Os)2 

Mono 

489.     Milarite  

HKCa2Al2(Si2Os)6 

Hexag 

490.     Eudidymite  

HNaBeSijOg 

Mono 

49  1      Epididymite 

HNaBeSi3O8 

Ortho 

492.     Orthoclase 

KAlSijOs 

IVIono 

493  .    Adularia 

KAlSijOg 

Mono 

494.    Valencianite     

KAlSi3O8 

IVIono 

495.     Sanidine  

KAlSijOg 

JVIono 

496.    Rhyacolite  

KAlSi3O8 

JVIono 

497.    Loxoclase  

KAlSijOg  •  7Na2O 

Mono 

498.     Murchisonite  

KAlSi3O8 

Mono. 

499.     Perthite 

KAlSi3O8 

Mono 

500.     Hyalophane 

(K2  Ba)Al2(SiO3)4 

Mono 

501.     Microcline 

KAlSi3O8 

Triclinic 

502.    Amazonstone  . 

KAlSi3O8 

Triclinic 

503.     Chesterlite  

KAlSi3O8 

Triclinic 

504.     Anorthoclase  

KAlSi3O8 

Triclinic 

505.     Albite  

NaAlSi3O8 

Triclinic 

506.     Peristerite  

NaAlSi3O8 

Triclinic 

507.     Pericline 

NaAlSi3O8 

Triclinic 

508.     Cleavelandite 

NaAlSi3O8 

Triclinic 

509.     Oligoclase  

*Ab3Ani 

Triclinic 

510.     Sunstone  

*Ab3Aih 

Triclinic 

511.    Andesine  

*Ab3Ant 

Triclinic 

512.    Labradorite  

*AbjAnz 

Triclinic 

513      Maskelynite 

*Ab3Ani 

Grains 

514.    Anorthite 

CaAl2Si2O8 

Triclinic 

515.    Indian!  te 

CaAl2Si2O8 

Triclinic 

516.    Cyclopite     

CaAl2Si2O8 

Triclinic 

517.     Celsian  

BaAl2Si2O8 

Triclinic 

b.  Metasilicates 
518.    Leucite  

KAl(SiO3)a 

Ortho. 

519.    Pollucite  

H2Cs4Al4(SiO3)9 

Regular 

520.     Enstatite 

MgSiO3 

Ortho. 

521.     Chladnite 

MgSiO3 

Ortho. 

522.     Bronzite  

MgSiO3 

Ortho. 

523.    Hypersthene  

(Fe,Mg)SiO3 

Ortho. 

524.    Bastite  

(Fe,Mg)SiO3 

Ortho. 

525.     Peckhamite 

2(Mg  Fe)SiO3-(Mg,Fe)SiO4 

Ortho. 

526.     Pyroxene 

Ca(Mg,Fe)Si2O6  •  (Mg,Fe)  (AlFe)2Si2O6 

Mono. 

527.     Diopside       

CaMg(SiO3)2 

Mono. 

528.     Malacolite  

CaMg(SiO3)2 

Mono. 

529.     Alalite  

CaMg(SiO3)2 

Mono. 

530.    Traversellite 

CaMg(SiO3)2 

Mono. 

53  1  .    Violan 

CaMg(SiO3)2 

Mono. 

*  Ab = Albite ;  An  =  Anorthite. 


COMPREHENSIVE  LIST  Of*  MINERALS 
LIST  OF  MINERALS 


231 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

488. 

Colorless 

6 

2 

Massachusetts 

Lithium 

489. 

Colorless 

5 

2-5 

Switzerland. 

Potassium 

490. 

White 

6 

2-5 

Norway 

491. 

White 

5-5 

3-5 

South  Greenland 

492. 

Colorless 

6 

2-5 

California 

493- 

Colorless 

6 

2-5 

Switzerland 

494. 

Colorless 

6 

2-5 

Valencia 

495- 

Colorless 

6 

2-5 

Valencia 

496. 

Colorless 

6 

2.5 

Monte  Somma 

497- 

Colorless 

6 

2.5 

New  York 

498. 

Red 

6 

2.5 

England 

499- 

Red 

6 

2-5 

Ontario 

500. 

Red 

6 

2.8 

Sweden 

501. 

White 

6 

2.5 

Pike's  Peak 

502. 

White 

6 

2.5 

Pike's  Peak 

SOS- 
504. 

White 
White 

6 
6 

2.5 

2-5 

Pennsylvania 
Pennsylvania 

•Rock  forming 

505- 

White 

6 

2.6 

E.  United  States 

506. 

White 

6 

2.6 

E.  United  States 

So?- 

White 

6 

2.6 

E.  United  States 

508. 

Bluish 

6 

2.6 

New  Hampshire 

509- 

White 

6 

2.6 

New  York 

510. 

White 

6 

2.6 

Norway 

SIL 

White 

5 

2.6 

Rocky  Mts. 

512. 

Gray 

5 

2.7 

New  York 

5J3- 

Colorless 

5 

2.7 

Meteorites 

Si4. 

White 

6 

2.7 

Mt.  Vesuvius 

5i5- 

White 

6 

2-7 

India 

516. 

White 

6 

2.7 

Cyclopean  Island 

5i7. 

Colorless 

6 

3 

Sweden 

518. 

Colorless 

5-5 

2.5 

Vesuvius 

Si9. 

White 

6-5 

2.9 

Maine 

520. 

Gray 

5-5 

3 

New  York 

521. 

Gray 

5-5 

3 

Meteorites 

522. 

Green 

5-5 

3 

New  York 

523- 

Brownish  green 

5 

3 

New  York 

524- 
525- 

Green 
Yellow 

3-5 

2-5 

3-2 

Hartz 
Meteorites 

Rock  forming 

526. 

White 

5 

3 

Igneous  rocks 

527- 

Light  green 

5-5 

3-3 

Igneous  rocks 

528. 

Light  green 

5-5 

3-3 

Sweden 

529- 

Green 

5-5 

3-3 

Piedmont 

530. 

Green 

5-5 

3-3 

Traversella 

531- 

Blue 

5-5 

3-3 

Italy 

232 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 


Form 


VII.  SILICATES — continued 

532.  Canaanite 

533.  Lavrovite 

534.  Hedenbergite 

535.  Sahlite 

536.  Baikalite 

537.  Coccolite 

538.  Diallage ." 

539.  Omphacite 

540.  Schefferite 

541.  Jeffersonite 

542.  Augite 

543.  Leucaugite 

544.  Fassaite 

545.  Acmite 

546.  Spodumene 

547.  Hiddenite 

548.  Jadeite 

549.  Chloromelanite 

550.  Nephrite 

551.  Wollastonite 

552.  Pectolite 

553.  Rosenbuschite 

554.  Wohlerite 

555.  Lavenite 

556.  Rhodonite 

557.  Bustamite 

558.  Fowlerite 

559.  Babingtonite 

560.  Hiortdahlite 

561.  Anthophyllite 

562.  Gedrite 

563.  Amphibole 

564.  Tremolite 

565.  Actinolite 

566.  Nephrite 

567.  Asbestus,  amianthus. . 

568.  Mountain  leather .  . . . 

569.  Mountain  cork 

570.  Smaragdite 

571.  Uralite 

572.  Cummingtonite 

573.  Dannemorite 

574.  Griinerite 

575.  Richterite 

576.  Breislakite 

577.  Hornblende..... 

578.  Edenite 

579.  Koksharovite 

580.  Pargasite 


CaMg(Si03)2 

CaMg(Si03)2 

CaFe(SiO3)2 

CaFe(SiO3)2 

CaFe(Si03)2 

CaFe(Si03)2 

CaFe(SiO3)2 

CaFe(SiO3)2 

CaMg(Fe,Mn)(SiO3)2 

Like  schefferite+Zn 

CaMg(Si03)2 

CaMg(Si03)2 

CaMg(Si03)2 

NaFe(Si03)2 

LiAl(Si03)2 

LiAl(SiO3)2 

NaAl(SiO3)2 

NaAl(SiO3)2 

NaAl(SiO3)2 

CaSiO3 

HNaCa2(Si03)3 

6CaSiO3-  2Na2ZrO2F2-  (TiSiO3TiO3) 

CaIONa5Fe3Nb2Zr3Sii0O42 

(Na,Ca,Mn,Fe)  (F,Zr,O)Si2O6 

MnSiO3 

Like  rhodonite +Fe,Ca 

Like  rhodonite+Fe,Ca,Zn 

(Ca,Fe,Mn)Si03 

(Na2,Ca)(Si,Zr)03 

(Mg,Fe)Si03 

Like  anthophyllite+Al 

CaMgFe[MnNa2K2H2(SiO3)4] 

CaMg3(Si03)4 

Like  tremolite+Fe 

CaMg3(Si03)4 

CaMg3(Si03)4 

CaMg5(Si03)4 

CaMg3(Si03)4 

CaMg3(Si03)4 

CaMg3(Si03)4 

Like  actinolite+Mg 

Like  actinolite+Mn 

FeSiO3 

(K2,Na2,Mg,Ca,Mn,Fe)4(Si03)4 

(K2,Na2,Mg,Ca,Mn)4(Si03)4 

Ca(MgFe)3Si03)4-  CaMg2Al2(Si04)3 

Ca(MgFe)3Si03)4-  CaMg2Al2(Si04)3 

Ca(MgFe)3Si03)4-  CaMg2Al2(Si04)3 

Ca(MgFe)3Si03)4-  CaMg2Al2(SiO4)3 


Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Mono. 

Triclinic 

Triclinic 

Triclinic 

Triclinic 

Triclinic 

Ortho. 

Ortho. 

Mono. 

Mono. 

Mono. 

Compact 

Fibrous 

Fibrous 

Fibrous 

Fibrous 

Fibrous 

Fibrous 

Fibrous 

Fibrous 

Fibrous 

Fibrous 

Mono. 

Mono. 

Mono. 

Mono. 


COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


233 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

S32- 

Gray 

5- 

3-3 

Connecticut 

533- 

Green 

5- 

3-3 

East  Siberia 

534- 

Black 

5- 

3-5 

Sweden 

535- 

Green 

5- 

3-5 

Sweden 

536. 

Green 

5- 

3-5 

Siberia 

537- 

Dark  green 

4 

3 

Mountains 

538. 

Green 

4 

3 

Mountains 

539- 
540. 

Brown 
Brown 

4 
4 

3 
3 

Mountains 
Mountains 

•Rock  forming 

541- 

Dark 

6 

3 

New  Jersey 

542. 

Green 

5-5 

3-3 

E.  United  States 

543- 

White 

6-5 

3 

E.  United  States 

544- 

Green 

6-5 

3 

Vesuvius 

545- 

Gray 

6 

3-5 

Colorado 

546. 

Green 

6-5 

3 

Massachusetts 

547- 

Green 

6-5 

3 

Massachusetts 

548. 

Green 

6-5 

3 

Asia 

Ornaments 

549- 

Dark  green 

6-5 

3 

Asia 

Rock  forming 

550. 

Green 

6-5 

3 

Asia 

Ornaments 

551- 

White 

4-5 

2.8 

New  York 

552. 

White 

5 

2.6 

New  Jersey 

553- 

White 

5 

2.6 

Norway 

Rock  forming 

554- 

Yellow 

5-5 

3-4 

Norway 

555- 

Yellow 

6 

3-5 

Norway 

556. 

Red 

6 

3-5 

Russia 

557- 

Red 

6 

3-5 

Mexico 

• 

558. 

Red 

6 

3-5 

New  Jersey 

Ornaments 

559- 

Black 

5-5 

3 

Norway 

560. 

Yellow 

5-5 

3 

South  Norway 

561. 

Brown 

5-5 

3 

North  Carolina 

562. 

Brown 

5-5 

3 

North  Carolina 

563. 

Green 

5 

2-9 

Mountains 

Rock  forming 

564. 

Gray 

5 

2-9 

Mountains 

565- 

Green 

5 

3 

Mountains 

566. 

Green 

6 

2-9 

Mexico 

Ornaments 

567- 

Gray 

3 

2-9 

Mountains 

) 

568. 

Gray 

3 

2-9 

Mountains 

Cloth 

569- 

Gray 

3 

2-9 

Mountains 

J 

570. 

Green 

3 

2.9 

Alps 

•  . 

571- 

Green 

3 

2.9 

Alps 

572. 

Gray 

3 

3 

Massachusetts 

573- 

Brown 

3 

3 

Sweden 

574- 

Brown 

3 

3-7 

Sweden 

575- 

Brown 

3 

3-7 

Sweden 

Rock  forming 

576. 

Brown 

3 

3-7 

Vesuvius 

577- 

Black 

5-5 

3 

Vesuvius 

578. 

Gray 

5-5 

3 

New  York 

579- 

Gray 

5-5 

3 

New  York 

58o. 

Green 

5-5 

3 

Finland 

234 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

VII.     SILICATES  —  continued 
581.     Kataforite   

Ca(MgFe)3(SiO3)4-  CaMg2Al2(SiO4)3 

Mono. 

582.     Kupfferite  

Ca(MgFe)3(SiO3)4  •  CaMg2Al2(SiO4)3 

Mono. 

583.     Syntagma  tite  

Ca(MgFe)3(SiO3)4-CaMg2Al2(SiO4)3 

Mono. 

584.     Bergamaskitc 

Ca(MgFe)3(SiO3)4-CaMg2Al2(SiO4)3 

Mono. 

585.    Kaersutite       .... 

.(-Mg)  m 
Like  amphibole-|-Ti 

Mono. 

586.    Hastingsite  

Contains  much  Na 

Mono. 

587.     Glaucophane  

NaAl(SiO3)2-  (Fe,Mg)SiO3 

Mono. 

588      Gastaldite 

NaAl(SiO3)2-  (Fe  Mg)SiO3 

Mono. 

5880    Riebeckite 

2NaFe(SiO3)2-FeSiO3 

Mono. 

589.     Crocidolite 

NaFe(SiO3)2-FeSiO3 

Mono. 

590.    Abriachanite 

NaFe(SiO3)2-FeSiO3 

Amor. 

5Qoa.  Arfvedsonite   .    . 

4Na2O  •  3CaO  •  i4FeO  •  (Al,Fe)203  •  2  iSiO2 

Mono. 

591.     Crossite        

Like  arfvedsonite+Na 

Mono. 

592.    Barkevikite  

Like  arfvedsonite+Na 

593.     Aenigmatite  

Na4Fe,,AlFe(SiTi)i2O38 

Triclinic 

^94.    Beryl.  . 

Be3Al2Si6Oi8 

Hexag. 

595.     Emerald. 

Be3Al2Si6Oi8 

Hexag. 

596.    Aquamarine 

BejAlaSieOig 

Hexag. 

597.     Davidsonite         .  .    . 

Be3Al2Si6Oi8 

Hexag. 

598.     Eudialyte  

NaI3(Ca,Fe)6Cl(Si,Zr)20OS2 

Hexag. 

599.     Eucolite   

NaI3(Ca,Fe)6Cl(Si,Zr)2oOs2 

Hexag. 

600.    Elpidite  

Na2O  •  ZrO2  •  6SiO2  •  3H2O 

601.     Catapleiite  

H4(Na2,Ca)ZrSi3On 

Hexag. 

602      Cappelenite 

3BaSiO3  •  2Y2(SiO3)3  •  sYBO3 

Hexag. 

603.     Melanocerite 

i2(H2Ca)SiO3-3(Y,Ce)BO3-2H2(Th,Ce) 

Hexag. 

604.     Caryocerite   

O2F2-8(Ce,La,Bi)OF 
6(H2,Ca)Si03  •  2  (Ce,Da,Y)BO3  •  3H2(Ce, 

Hexag. 

605.     Streenstrupine  
606.    Tritomite 

Th)02F2-2LaOF 
Ti,Th,Ce^,La,Di,Al,Fe,Mn,Ca,Na,H, 
silicate 
2(H2Na2Ca)SiO3-  (Ce,La,Di,Y)BO3- 

Hexag. 

607.    Leucophanite  

H2(Ce,Th,Zr)02F 

Na(BeF)Ca(SiO3)2 

Hexag. 
Ortho. 

608.    Meliphanite  

NaCa2Be2FSi3Oi0 

Tetrag. 

609.    lolite  

H2(Mg,Fe)4Al8Sii0O37 

Ortho. 

610.     Bonsdorffite  
611.     Fahlunite             .    .    . 

H2(Mg,Fe)4Al8Sii0O,7,  altered 
H2(Mg,Fe)4Al8Sii0O37,  altered 

Ortho. 
Ortho. 

612.    Pyrargillite     

H2(Mg,Fe)4Al8SiioO37,  altered 

Ortho. 

613.     Esmarkite  

H2(Mg,Fe)4Al8SiIOO37,  altered 

Ortho. 

614.     Raumite  

H2(Mg,Fe)4Al8Sii0O37,  altered 

Ortho. 

615      Chlorophylli  te 

H2(Mg,Fe)4Al8Sii0O37,  altered 

Ortho. 

6  1  6.    Aspasiolite 

H2(Mg,Fe)4Al«SiioO37,  altered 

Ortho. 

617.    Polychroilite  
618.     Barysilite  

H2(Mg,Fe)4Al8SiI0037,  altered 
Pb3Si2O7 

Ortho. 

619.     Ganomalite  

Pb3Si2O7-(Ca,Mn)2SiO4 

Tetrag. 

(Pb  Ba  Ca)  B2(SiO3)i2 

621      Barylite 

Ba4Al4Si7O24 

622      Roeblingite 

5(H2CaSiO4)  •  2(CaPbSO4) 

c.  Orthosilicates 
623      Nephelite 

K2Na6Al«Si9O24 

Hexag. 

624     Elaeolite 

K2Na6Al«Si9O24 

Hexag. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


235 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

58i. 

Green 

5-5 

3 

Norway 

582. 

Deep  green 

5-5 

3 

Tunkinsk  Mts. 

583. 

Black 

5-5 

3 

Vesuvius 

584. 

Black 

5-5 

3 

Italy 

585. 

Brown 

5 

3 

North  Greenland 

586. 

Brown 

5 

3 

Ontario 

587. 
588. 

Blue 
Blue 

6 
6 

3 
3 

California 
Corsica 

Rock  forming 

5880. 

Black 

6 

3 

Ireland 

589- 

Blue 

4 

3 

Rhode  Island 

59°- 

Blue 

4 

3 

Scotland 

SQoa. 

Black 

6 

3 

Colorado 

591- 

Black 

6 

3 

California 

592. 

Black 

6 

3 

Southern  Norway 

CQ2 

Black 

a 

Southern  Norway 

oVO* 
594- 

Green 

7-5 

2.6 

E.  United  States 

) 

595- 

Green 

7-5 

2.6 

E.  United  States 

^Gems 

596. 

Green 

7-5 

2.6 

E.  United  States 

/ 

597- 

Green 

7-5 

2.6 

Scotland 

. 

598. 

Red 

5 

2.9 

Western  Greenland 

599- 

Red 

5 

2.9 

Norway 

600. 

2    S 

South  Greenland 

601. 

Yellow 

6 

•  o 

2.8 

Norway 

602. 

Brown 

6 

4.4 

Norway 

603. 

Brown 

6 

4 

Norway 

604. 

Brown 

6 

4 

Norway 

605. 

Brown 

4 

3 

Greenland 

606. 

Brown 

5 

4 

Norway 

607. 

Green 

4 

2.9 

Norway 

608. 

Yellow 

5 

3 

Norway 

Rock  forming 

609. 

Blue 

7 

2.6 

Connecticut 

610. 

Blue 

7 

2.6 

Finland 

611. 

Various 

7 

2.6 

Sweden 

612. 

Various 

7 

2.6 

Helsingfors 

613.- 

Various 

7 

2.6 

Norway 

614. 

Various 

7 

2.6 

Finland 

615- 

Various 

7 

2.6 

Maine 

616. 

Various 

7 

2.6 

Kragero 

617. 

Various 

7 

2.6 

Kragero 

618. 

White 

3 

6 

Sweden 

619. 

Colorless 

3 

5-7 

Sweden 

620. 

White 

5 

3-8 

Sweden 

621. 

Colorless 

7 

4 

Sweden 

622. 

White 

3 

3 

New  Jersey 

623. 
624. 

Colorless 
Brown 

5 
5 

2-5 

2-5 

Vesuvius 
Maine 

rRock  forming 

236 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 


Form 


VII.  SILICATES — continued 

625.  Gieseckite 

626.  Eucryptite , 

627.  Kaliophilite 

628.  Cancrinite  

629.  Microsommite 

630.  Sodalite 

631.  Haiiynite 

632.  Noselite 

633.  Lazurite 

634.  Helvite 

635.  Danalite 

636.  Eulytite 

637.  Zunyite 


638.  Garnet 

639.  Grossularite 

640.  Cinnamon-stone .... 

641.  Hyacinth 

642.  Succinite 

643.  Romanzovite 

644-  Pyrope 

645.  Rhodolite 

646.  Almandite 

647.  Spessartite 

648.  Andradite 

649.  Topazolite 

650.  Demantoid 

651.  Colophonite 

652.  Melanite 

653.  Pyreneite 

654.  Rothoffite 

655.  Allochroite 

656.  Polyadelphite 

657.  Bredbergite 

658.  Aplome 

659.  Titaniferous  garnet. . 

660.  Yttergranat 

661.  Uvarovite 

662.  Schorlomite 

663.  Partschinite 

664.  Agricolite 

665.  Chrysolite 

666.  Olivine 

667.  Hyalosiderite 

668.  Iddingsite 

669.  Monticellite 

670.  Forsterite 

671.  Hortonolite 


K2Na6Al8Si9O24-nH2O 

LiAlSi04 

KAlSiO4 

H6Na6Ca(NaC03)2Als(SiO4)9 

(Na,K)i0Ca4AlI2SiI2OS2SCl4 

Na4(AlCl)Al2(SiO4)3 

Na2Ca2(NaSO4-Al)Al2(SiO4)3 

Na4(NaSO4-Al)Al2(Si04)3 

Na4(NaS3-Al)Al2(Si04)3 

(Mn,Fe)2(Mn2S)Be3Si04)3 

(Fe,Zn,Mn)2[(Zn,Fe)2S]Be3(Si04)3 

Bi4(Si04)3 

(Al(OH,F,Cl)2)6Al2(Si604)3 

II  III 

R3R2(SiO4)3 

Ca3Al2(Si04)3 

Ca3Al2(Si04)3 

Ca3Al2(Si04)3 

Ca3Al2(Si04)3 

Ca3Al2(Si04)3 

Mg3Al2(Si04)3 

Mg3Al2(Si04)3 

Fe3Al2(SiO4)3 

Mn3Al2(Si04)3 

Ca3Fe2(Si04)3 

Ca3Fe2(Si04)3 

Ca3Fe2(Si04)3 

Ca3Fe2(Si04)3 

Ca3Fe2(SiO4)3 

Ca3Fe2(SiO4)3 

(CaMg)3Fe2(SiO4)3 

(Mg,Ca3(Fe2(Si04)3 

(Mg,Ca)3Fe2(Si04)3 

(Mg,Ca)3Fe2(Si04)3 

(Mg,Ca)3Fe2(Si04)3 

3CaO-  (Fe,Ti,Al)203-3(Si,Ti)02 

3CaO-(Fe,Ti,Y,Al)YO3 

Ca3Cr2(SiO4)3 

Ca3(FeTi)2(SiTi)04)3 

(Mn,Fe)3Al2Si30I2 

Bi4Si3Ot2 

(Mg,Fe)2Si04 

(Mg,Fe)2SiO4 

(Mg,Fe)2Si04+Fe 

(Ca,Mg,Fe)2SiO4 

CaMgSiO4 

Mg2Si04 

(Fe,Mg,Mn)2Si04 


Pseudo. 

Hexag. 

Hexag. 

Hexag. 

Hexag. 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Regular 

Mono. 

Mono. 

Ortho. 

Ortho. 

Ortho. 

Ortho. 

Ortho. 

Ortho. 

Ortho. 


COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


237 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

625. 

Brown 

5 

2.6 

New  York 

626. 

Colorless 

5 

2.6 

Connecticut 

627. 

Colorless 

6 

2 

Mt.  Somma 

• 

628. 
629. 

Gray 
Colorless 

5 
5 

2 

2 

Maine 

Vesuvius 

Rock  forming 

630. 

Gray 

5 

2 

Maine 

631. 

Blue 

5-5 

2 

Vesuvius 

632. 

Grayish 

5-5 

2 

Andernach 

633. 

Blue 

5 

2 

Chile 

Ornaments 

634. 

Yellow 

6 

3 

Virginia 

635. 

Red 

5-5 

3 

Colorado 

636. 

Brown 

4-5 

6 

Saxony 

637. 

Brown 

7 

2.8 

Colorado 

638. 

Red 

6-5 

3 

Mountains 

639- 

Pale  green 

6-5 

3-5 

Ceylon 

640. 

Brown 

6-5 

3-5 

Ceylon 

641. 

Brown 

6-5 

3-5 

Ceylon 

642. 

Yellow 

6-5 

3-5 

Piedmont 

643- 
644. 

Brown 
Red 

6-5 
6.5 

3-5 
3-7 

Russia 
Bohemia 

Rock  forming 

645- 

Red 

6-5 

3-7 

North  Carolina 

646. 

Red 

6-5 

3-9 

Pennsylvania 

647. 

Red 

6-5 

4 

Colorado 

648. 

Yellow 

6-5 

3-8 

Portugal 

649. 

Green 

6-5 

3-8 

France 

650. 

Green 

6-5 

3-8 

Mountains 

651. 

Brown 

6-5 

3-8 

Mountains 

652. 

Black 

6-5 

3-8 

Mountains 

653- 

Black 

6-5 

3-8 

Mountains 

654- 

Brown 

6-5 

3-8 

Mountains 

655. 

Brown 

6-5 

3-8 

Mountains 

656. 

Yellowish  brown 

6-5 

3-8 

New  Jersey 

(Rock  forming 

657- 

Yellowish  brown 

6-5 

3-7 

Sala 

and  gems 

658. 

Brown 

6-5 

3-7 

Siberia 

659- 

Black 

6-5 

3-7 

Siberia 

660. 

Black 

6-5 

3-7 

Norway 

661. 

Green 

7-5 

3 

Canada 

Rock  forming 

662. 

Black 

7 

3-8 

Arkansas 

663. 

Yellow 

6-5 

4 

Transylvania 

664. 

Yellow 

2 

Johanngeorgen  . 

Bismuth 

665. 

Green 

6-5 

3 

Virginia 

666. 

Green 

6-5 

3 

Virginia 

667. 

Green 

6-5 

3 

Baden 

668. 

Brown 

2.8 

California 

Rock  forming 

669. 

Gray 

5 

3 

Arkansas 

670. 

White 

6 

3 

Vesuvius 

671. 

Yellow 

6 

3-9 

New  York 

238 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

VII.    SILICATES  —  continued 
672.     Fayalite  

Fe2SiO4 

Ortho 

673.     Knebelite  

(Fe,Mn)2SiO4 

Ortho 

674.    Tephroite  

Mn2SiO4 

Ortho 

675.    Willemite  

Zn2SiO4 

Hexag 

676     Phenacite 

Be2SiO4 

Hexasr 

677     Trimerite 

(Mn,Ca)2SiO4  •  Be2SiO4 

Triclinic 

678     Dioptase          ... 

H2CuSiO4 

Hexaiz 

679.     Friedelite   

H7(MnCl)Mn4Si4Oi6 

Hexag 

680.     Pyrosmalite  

H7([Fe,MnJCl)  (Fe,Mn)4Si4Oi6 

Hexag 

681.     Meionite  

Ca4AkSi<As 

Tetrag 

682.    Wernerite  

*Me,Ma2 

Tetrag. 

683.    Passauite  

*Me,Ma2  or  Ma3 

Tetrag. 

684     Glaucolite 

*Me  Ma2  or  Ma3 

Tetrae 

685      Mizzonite 

Me,Ma3 

Tetrag 

686      Dipyre 

Me,Ma5 

Tetrag 

687.     Couseranite 

Me,Ma3 

Tetrag 

688.     Marialite 

Na4Al3Si9O24Cl. 

Tetrag 

689.     Sarcolite 

Ca8Na2Al6Si9O36 

Tetrag. 

690.     Melilite        .  .        ... 

Na2(Ca,Mg)H(Al,Fe)4(SiO4)9 

Tetrag. 

691.    Humboldtilite   

Na2(Ca,Mg)XI(Al,Fe)4(SiO4)9 

Tetrag. 

692.     Gehlenite   

Ca3Al2Si2Oi0 

Tetrag. 

693  .    Vesuvianite  

H4Cai2(Al,Fe)6SIOO43 

Tetrag. 

694.     Cyprine  

H4CaI2(Al,Fe)6SIOO43 

Tetrag. 

695.     Zircon  

ZrSiO4 

Tetrag. 

696.     Hyacinth  

ZrSi04 

Tetrag. 

607.     Tareon 

ZrSiO4 

Tetrag. 

698.    Thorite 

ThSiO4 

Tetrag. 

699.    Auerlite 

ThSiO4 

Tetrag. 

700.    Danburite 

CaB2(SiO4)2 

Ortho. 

701.     Topaz  

Al2(F-OH)2SiO4 

Ortho. 

702.    Physalite  

Al2(F-OH)2SiO4 

Ortho. 

703.     Pyonite  

Al2(F-OH)2SiO4 

Ortho. 

704.    Andalusite  

Al2SiOs 

Ortho. 

705.     Chiastolite  

Al2SiOs 

Ortho. 

706.     Sillimanite 

Al2SiOs 

Ortho. 

707.     Cvanite 

Al2SiOs 

Triclinic 

708.    Datolite 

HCaBSiOs 

Mono. 

709.    Homilite  . 

(Ca,Fe)3B2Si2Ox0 

Mono. 

710.    Euclase  

HBeAlSiOs 

Mono. 

711.     Gadolinite  

Be2FeY2Si2Oi0 

Mono. 

712.     Yttrialite  

(ThY)2O3-2SiO2 

Amorph. 

713.     Rowlandite  

Y,Fe,U,Ca,  silicate    - 

Massive 

714.    Mackintoshite 

T,Ce,U,  silicate 

Massive 

715.    Zoisite 

HCa2Al3Si3Oi3 

Ortho. 

716.    Thulite 

HCa2Al3Si3OI3 

Ortho. 

717.     Epidote  

HCa2(Al,Fe)3Si3OI3 

Mono. 

718.     Scorza  

HCa2(Al,Fe)3Si3Ou 

Sand 

719.    Thallite 

HCa2(Al,Fe)3Si3Or3 

Mono. 

*Me  =  Meionite;  Ma = Marialite. 


COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


239 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

672. 

Brown 

6 

4 

Yellowstone  Park 

| 

673. 

Brown 

6 

4 

Sweden 

^Rock  forming 

674. 

Red 

5-5 

4 

New  Jersey 

j 

675- 

White 

5-5 

3-8 

New  Jersey 

Zinc 

676. 

Colorless 

7-5 

2.9 

Colorado 

Gems 

677- 

Pink 

6 

3 

Sweden 

678. 

Green 

5 

3 

Arizona 

679. 

Red 

4 

3 

Pyrenees 

680. 

Gray 

4 

3 

Sweden 

681. 

Colorless 

5-5 

2.7 

Vesuvius 

682. 

White 

5 

2.6 

Finland 

683. 

Yellowish 

5 

2.6 

Bavaria 

684. 

Gray 

5 

2.6 

Siberia 

685. 

White 

5 

2.6 

Vesuvius 

686. 

White 

5 

2.6 

Norway 

687. 

White 

5 

2.6 

Pyrenees 

688. 
689. 

White 
Red 

6 

2.6 

2-5 

Naples 
Vesuvius 

Rock  forming 

690. 

White 

5 

2.9 

Vesuvius 

691. 

Yellow 

5 

2-9 

Vesuvius 

692. 

Green 

5 

2.9 

Tyrol 

693- 

Brown 

6-5 

3 

California 

694. 

Blue 

6-5 

3 

Norway 

695- 

Yellow 

7-5 

4-6 

New  York 

696. 

Red 

7-5 

4-6 

Canada 

697. 

Smoky 

7-5 

4.6 

Ceylon 

698. 

Black 

4-5 

5 

Norway 

699- 

Orange 

2-5 

4 

North  Carolina 

700. 

Yellow 

7 

2-9 

Connecticut 

701. 

Yellow 

8 

3 

Urals 

Gems 

702. 

Yellow 

8 

3 

Finbo 

703- 
704. 

Yellow 
Red 

8 
7-5 

3 
3 

Saxony 
E.  United  States 

70S- 

Brown 

7 

3 

Maine 

706. 

Brown 

6 

3 

E.  United  States 

707. 

Blue 

5 

3-5 

E.  United  States 

708. 

White 

5 

2.9 

New  Jersey 

709. 

Black 

5 

3 

Norway 

710. 
711. 

Colorless 
Black 

7-5 
6-5 

3 
4 

Brazil 
Texas 

Rock  forming 

712. 

Green 

5 

4-5 

Texas 

7i3- 

Drab  green 

4-5 

Texas 

714. 

Black 

Texas 

7i5- 

Gray 

6 

3 

Carinthia 

716. 

Red 

6 

3 

Carinthia 

717. 

Green 

6 

3 

Michigan 

718. 

Green 

6 

3 

Transylvania 

719. 

Yellow 

6 

3 

Bourg  d'Oisans 

240 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

VII.    SILICATES  —  continued 
720.     Bucklandite  

HCa2(Al,Fe)3Si3OI3 

Mono. 

721.    Withamite  

HCa2(Al,Fe)3Si3OI3 

Mono. 

722      Clinozoisite 

HCa2(Al,Fe,Mn)3Si3Oi3 

Miono 

723.    Picroepido  t6 

HCa2(Al,Fe,Mn)3Si3OI3 

Mono 

724.     Piedmonite 

HCa2(Al,Fe,Mn)3Si3OI3 

Mono. 

725.    Allanite 

Al,Fe,Mn,Ca,Na,K,Mg,Er,Y,La,Di,Ce, 

Mono. 

726.    Bagrationite  

Th,  silicate 
Al,Fe,Mn,Ca,Na,K,Mg,Er,Y,La,Di,Ce, 

Mono. 

727.    Axinite  

Th,  silicate 

H2(Ca,Mn)4(BO)Al3(SiO4)5 

Triclinic 

728.    Prehnite  

H2Ca2Al2(SiO4)3 

Ortho. 

720     Harstigite 

H7(Ca  Mn)I2Al3Sii0O40 

Ortho. 

730.     Cuspidinc 

Ca^iCO  F2)4 

Mono. 

d.  Subsilicates 
731.     Chondrodite  

H2(Mg,Fe)I9Si8O34F4 

Mono. 

732.     Humite  

H2(Mg,Fe)I9Si8O34F4 

Ortho. 

733.     Clinohumite 

H2(Mg  Fe)i9Si«O34F4 

Mono. 

724.     Ilvaite 

CaFe2(FeOH)(SiO4)2 

Ortho. 

735.    Ardennite 

HsMn4Al4VSi4O23 

Ortho. 

736.    Langbanite 

37MnsSiO7'  ioFe3Sb2O8 

Hexag. 

737.    Kentrolite  .          ... 

Pb2Mn2Si2O9 

Ortho. 

738.     Melanotekite  

Pb2Fe2Si2O9 

Ortho. 

739.     Bertrandite  

H2Be4Si2O9 

Ortho. 

740.     Calamine  

H2Zn2SiOs 

Ortho. 

741.     Clinohedrite  

H2CaZnSiOs 

Mono. 

742.     Carpholite  

H4MnAl2Si2OIO 

Mono. 

743     Lawsonitc 

H4CaAl2Si2Oi0 

Ortho. 

744.      Cerite 

Ce2(OH)3CeO-  CaFe(SiO3)3 

Ortho. 

745.    Tourmaline 

Fe4Na2B6AlI4H8Sii2O63 

Hexag. 

746.    Indicolite 

Fe4Na2B6AlI4H8Sii2O63 

Hexag. 

747.     Aphrizite        .    . 

Fe4Na2B6Ali4HgSii2O63 

Hexag. 

748.    Achroite       

(Fe4Na2B6AlI4H8SiI2O63),  etc. 

Hexag. 

749.     Dumortierite  

4Al2O3«3SiO2 

Ortho. 

750.     Staurolite  

HFeAlsSi2OI3 

Ortho. 

751.     Nordmarkite  

HFeAlsSi2OI3+Mg 

Ortho. 

752.     Kornerupine  

MgAl2SiO6 

Ortho. 

753.     Sapphirine 

MgsAlr2Si2O27 

Mono. 

2.  Hydrous 
a.  Zeolites 
754.     Inesite  

2(Mn,Ca)SiO3-H2O 

Triclinic 

755.     Ganophyllite  

MnyAkSisOze  •  6H2O 

Mono. 

756.    Okenite  

H2CaSi2O6-H2O 

Ortho. 

7<?7      Gvrolite 

H2Ca2(SiO3)3-H2O 

Ortho. 

7«c8.     ADODhvllite 

H7KCa4(SiO3)8  -45H2O 

Tetrag. 

7«?o.    Ptilolite 

(CaK2Na2)  AkSiO^  •  sH2O 

Mono. 

760.     Mordenite  

(CaK2Na2)  AUSiioO^  •  6H2O 

Mono. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


241 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

720. 

Black 

6 

3 

Bourg  d'Oisans 

721. 

Red 

6 

3 

Scotland 

722. 

Rose  red 

Ceylon 

l  &  t.  • 
723- 

Yellowish 

6 

3 

Siberia 

724. 

Brown 

6-5 

3 

Pennsylvania 

725. 

Brown 

5-5 

3 

Massachusetts 

Rock  forming 

726. 

Black 

6 

3-8 

Massachusetts 

727. 

Brown 

6-5 

3 

Maine 

728. 

Green 

6 

2.8 

Connecticut 

729. 

Colorless 

5-5 

3 

Sweden 

730- 

Red 

5 

2.8 

Mt.  Somma 

731. 

Yellow 

6 

3 

Mt.  Somma 

732. 

Yellow 

6 

3 

New  York 

733- 

Yellow 

6 

3 

New  York 

734- 

Iron  black 

5-5 

3-9 

Elba 

735- 

Yellow 

6.7 

3-6 

Belgium 

Rock  forming 

736. 

Black 

6-5 

4-9 

Sweden 

737- 

Brown 

5 

6 

Chile 

738. 

Black 

6-5 

5-7 

New  Mexico 

739- 

Colorless 

6 

2-5 

Colorado 

740. 

White 

4-5 

3 

New  Jersey 

Zinc 

741. 

Colorless 

5-5 

3 

New  Jersey 

742. 

Yellow 

5 

2-9 

Hartz 

743- 

Colorless 

3 

California 

744- 

Gray 

5-5 

4-8 

Sweden 

745- 

Black 

7 

2-9 

Maine 

746. 
747- 
748. 

Blue 
Black 
Colorless 

7 
7 

7 

2-9 

2-9 

2-9 

Maine 
Norway 
Elba 

Rock  forming 
and  gems 

749- 

Blue 

7 

3 

Arizona 

750. 

Brown 

7 

3-6 

New  Hampshire 

75i- 

Brown 

7 

3-6 

Sweden 

752. 

Colorless 

6-5 

3 

Greenland 

753- 

Green 

7-5 

3 

Greenland 

754- 

Red 

6 

3 

Germany 

755- 

Brown 

4 

2.8 

Sweden 

» 

756. 

White 

4-5 

2 

Iceland 

7^7- 

White 

California 

•Rock  forming 

/  o  /  * 

758. 

White 

4-5 

2 

New  Jersey 

7CQ. 

Colorless 

Colorado 

/  ov 

760. 

White 

3 

2 

Wyoming 

242 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

VII.     SILICATES  —  continued 
761.    Heulandite 

H4CaAl2(SiO3)6  •  3H2O 

762.     Brewsterite 

H4(Sr  Ba  Ca)Al2Si$Oi8'3H2O 

M^ono 

763.     Epistilbite 

H4CaAl2Si6Ol8-3H2O 

M!ono 

764.    Wellsite 

(Ba,CaK2)  Al2Si3OIO  •  3H2O 

M!ono 

76'?.     Phillipsite  ., 

(K2,Ca)  Al2Si4Oi2  •  4^H2O 

jyjono 

766.    Harmotome  

H2(K2,Ba)  Al2SisOiS  •  4H2O 

M^ono 

767.     Stilbite  

H4(Na2,Ca)  Al2Si<iOl8  •  4H2O 

M!ono 

768.     Gismondite.  

CaAl2Si4OM-4H2O 

Mono. 

760     Laumontite 

H4CaAl2Si4OI4  •  2H2O 

M!ono 

770.    Leonhardite 

H4CaAl2Si4Oi4-2H2O 

M^ono 

771.     Schneider!  te  .... 

H4CaAl2Si4Oi4-  2H2O 

]Mono 

772.    Laubanite  

Ca2  Al2SisOIS  +  6H2O 

M!ono 

773.     Chabazite  

(Ca,Na2)  Al2Si4OI2  •  6H2O 

Hexag 

774.    Acadialite  

(Ca,Na2)  Al2Si4OI2  •  6H2O 

Hexag. 

775.    Haydenite  

(Ca,Na2)  Al2Si4OI2  •  eHaO 

Hexag. 

776.    Phacolite  

(Ca,Na2)  Al2Si4Oi2  •  6H2O 

Hexag. 

777.    Herschelite 

(Ca  Na2)Al2Si4Oi2*6H2O 

Hexajr 

778.     Gmelinite 

(Na2  Ca)Al2Si4OI2-6H2O 

Hexag 

779.    Levynite 

CaAl2Si3Oi0-5H2O 

Hexag 

780.     Offretite 

(K2Ca)2Al3Sii4O39  •  1  7H3O 

Hexag. 

781.    Analcite  

NaAlSi2Oe-H2O 

Regular 

782.     Analcime  

NaAlSi2O6-H2O 

Regular 

783.     Edingtonite  

BaAl2Si3OIO-3H2O 

Tetrag 

784.     Natrolite  

Na2Al2Si3OIO-2H2O 

Ortho. 

785.     Bergmannite  

Na2Al2Si3Oi0-2H2O 

Ortho. 

786.     Scolecite 

CaAl2Si3Oi0  •  3H2O 

M^ono 

787.     Mesolite 

CaAl2Si3Oi0  •  3H2O+Na2Al2Si3Oi0'  2H2O 

Mono. 

788.    Thomsonite  
789.     Ozarkite 

(Na2,Ca)Al2Si2O8-2iH20 
(Na2,Ca)  Al2Si2O8  •  2|H2O 

Ortho. 
Ortho. 

790.    Hydronephelite  
b.  Micas 
791.     Muscovite  

HNa2Al3Si3OI2-3H2O 
H2KAl3Si3OI2 

Ortho. 
Mono. 

792.     Damourite  

H2KAl3Si3OI2 

Mono. 

793.     Margarodite  

H2KAl3Si3OJ2 

Mono. 

794.     Gilbert!  te 

H2KAl3Si3Oi2 

Mono. 

795.     Sericite 

H2KAl3Si,OI2 

Scaly 

796.     Fuchsite 

H2KAl3Si3Oi2+Cr 

Scaly 

797.    Pinite  

H2KAl3Si,OI2 

Amorph. 

798.     Paragonite  

H2NaAl3(Si3OI2)3 

Mono. 

799.    Lepldolite  

(Li,K,Na)2(Al,Fe)OH2(Si03)3 

Mono. 

800.    Zinnwaldite 

H2K4Li4Fe3Al8F8SiI4O42 

Mono. 

801.     Biotite 

(H  K)2(Mg  Fe)4(Al,Fe)2(SiO4)4 

Mono. 

802.    Meroxene 

(H,K)2(Mg,Fe)4  Al,Fe)2(SiO4)4+Fe 

Mono. 

803.    Anomite     

(H,K)2(Mg,Fe)4  Al,Fe)2(SiO4)4-fMn 

Mono. 

804.    Haughtonite  

(H,K)2(Mg,Fe)4  Al,Fe)2(SiO4)4+Mn 

Mono. 

805.    Manganophyllite  
8q6.     Caswellite  

(H,K)2(Mg,Fe)4(Al,Fe)2(SiO4)4+Mn 
(H,K)2(Mg,Fe)4(Al,Fe)2(SiO4)4+Fe 

Mono. 
Mono. 

807.     Phlogopite 

(H  K)2(Mg  Fe)4(Al,Fe)2(SiO4)4+Fe 

Mono. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


243 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

761. 

White 

3-5 

2 

New  Jersey 

762. 

White 

5 

2 

Strontian 

763. 

White 

4 

2 

Nova  Scotia 

764. 

Colorless 

4 

2 

North  Carolina 

765. 

White 

4 

2 

Ireland 

766. 

White 

4-5 

2 

New  York 

767. 

White 

3-5 

2 

New  York 

768. 

Colorless 

4-5 

2 

Mt.  Albano 

769. 

White 

3-5 

2 

New  Jersey 

770. 

White 

3-5 

2 

Mountains 

771. 

White 

3-5 

2 

Italy 

772. 

White 

4-5 

2 

Silesia 

773- 

White 

4 

2 

New  Jersey 

774- 

Red 

4 

2 

Nova  Scotia 

775- 
776. 

Yellow 
Colorless 

4 
4 

2 
2 

Maryland 
Bohemia  - 

Rock  forming 

777- 

Colorless 

4 

2 

Sicily 

778. 

White 

4-5 

2 

New  Jersey 

779- 

White 

4 

2 

Colorado 

780. 

Colorless 

2 

France 

781. 

Colorless 

s 

2 

New  Jersey 

782. 

Colorless 

5 

1.9 

New  Jersey 

783- 

White 

4 

2.6 

Scotland 

784. 

White 

5 

2 

New  Jersey 

785. 

White 

S 

2 

Southern  Norway 

786. 

White 

5 

2 

Colorado 

787. 

White 

5 

2 

Colorado 

788. 

White 

s 

2 

Colorado 

789. 

White 

2 

Arkansas 

/  wy  * 

790. 

White 

4-5 

2 

Maine 

791. 

Colorless 

2 

2.7 

Maine 

792. 

Colorless 

2 

2.7 

Maine 

793- 

Pearly 

2 

2.7 

Tyrol 

794- 

Whitish 

2 

2-7 

Cornwall 

795- 

Whitish 

2 

2-7 

Wiesbaden 

796. 

Green 

2 

2-7 

Zillerthal 

797- 
798. 
799- 

Gray 
Yellow 
Red 

2-5 
2-5 
2-5 

2.6 
2.7 
2.8 

Germany 
Pennsylvania 
Maine 

Electrical 
purposes 

800. 
801. 
802. 

Yellow 
Green 
Dark 

2-5 
2.S 
2-5 

2.8 

2.7 
2.7 

Zinnwald 
N.  England  States 
Vesuvius 

and 
rock  forming 

803. 

Dark 

New  Jersey 

«  ^ 
804. 

2    0 

Sutherland 

ISW^J.. 

805. 

Red 

2-5 

*  *y 

2.7 

Sweden 

806. 

New  Jersey 

807. 

Brown 

2-5 

2.7 

New  York 

244 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

VII.     SILICATES  —  continued 
808      Lepidomelane 

(H  K),Fe»(Fe  AVhCSiO.L 

809      Alurgite 

(H  K)2Fe3(Fe  Al)4(SiO4)5+Mn 

M!ono 

810      Roscoelite 

H8K(Mg,Fe)(Al  V)4(SiO,)I2 

M^ono 

811      Margarite          

H2CaAl4Si2Oi2 

M^ono 

812      Seybertite  

H3(Mg,Ca)6AlsSi2Oi8 

M!ono 

813.     Zanthophyllite  

H8  (Mg,  Ca)  14  AlrfSijOa 

]VTono 

814.     Chloritoid  

H2(Fe,Mg)Al2SiO7 

Mono 

815.     Sismondine  

HiaFe^USisO,^ 

Triclinic 

816.     Salmite  

Hi4Fe7All6SisOS4 

Triclinic 

817      M^asonite 

Hi4Fe7AlI6Si8Os4 

Triclinic 

818      Ottrelite 

H2(Fe  Mn)Al2Si2O9 

Mono 

819      Venasquite 

H2FeAl2Si3On 

M^ono 

820      Phyllite 

H2FeAl2Si3On 

M^ono 

821      Clinochlore     

H8(Mg,Fe)sAl2Si3Oi8 

Mono 

822.     Leuchtenbergite  .  .    . 

H8(Mg,Fe)sAl2Si3Oi8,  lacks  Fe 

Mono 

823.     Kotschubeite  

H8  (Mg,  Fe)  ,  Al2Si3Ol8  +  Cr 

Hexag. 

824.     Manganchlorite  
825.     Penninite  

H8(Mg,Fe)5Al2Si3Ol8+Mn 
H8(Mg,Fe)5Al2Si3Ol8 

Hexag. 

Mono. 

826.     Kammererite  

H8(Mg,Fe)5Al2Si3Ol8 

Mono. 

827.     Pseudophite  
828.     Prochlorite  
829.     Cortmdophilite  .  .  .  .    : 
830      Amesite      

H8(Mg,Fe)5Al2Si3Ol8 
H40(Fe,Mg)23AlI4SiI3O9o 
HaoMgnAlsSiAs 
H4(Mg,Fe)2Al2SiO9 

Massive 
Mono. 
Mono. 
Hexag.. 

83  1  .     Aphrosiderite  

H10Fe6(Fe,Al)4Si4O25 

Hexag. 

832.     Diabantite  

Hl8(Fe,Mg)I2Al4Si9O45 

Hexag. 

833.     Delessite  

HIO(Mg,Fe)4(Al,Fe)4Si4O23 

Hexag. 

834.     Epichlorite  

H7(Mg,K2)7(Al,Fe)5Si4Ol8  ' 

Hexag. 

8  3  "5      Euralit6 

Hl6(Mg  Fe  Ca)9(Al  Fe)4Si9O37 

Amorph. 

836.     Chlorophaeite  

Fe,Mg,Mn,Ca,  silicate 

Amorph. 

837      Hullite 

Fe,Mg,Mn,Ca,  silicate 

Massive 

838.     Cronstedite  
839      Thuringite     

H6(Fe,Mg)3Al2Si20I3 
Hl8Fe8(Al,Fe)8Si<Ai 

Hexag. 

Massive 

840.     Chamosite     

H6(Fe,Mg)3Al2Si2Oi3 

Oolitic 

841.     Stilpnomelane  
842.     Strigovite  

2(Mg,Fe)0.(Fe,Al)203.5Si02.3H20 
H4Fe2(Al,Fe)2Si2OIt 

Scaly 
Hexag. 

843      Ru.mpfi.t6 

H28Mg7AlI6SiIOO6S 

Massive 

844     Vermiculite 

H24MgI2(Al  Fe^SicAs 

Crystal. 

845.    Jefferisite  
c.  Serpentine,  Talc 
846      Serpentine         

HI2Mg4(Al,Fe,)4Sis026 
H4Mg,Si2O0 

Crystal. 
Mono. 

847      Bastite       

H4Mg3Si2O9 

Massive 

848.     Retinalite  

H4Mg3Si2O9+3  per  cent  H2O 

Massive 

849      Bowenite 

H4Mg3Si2O9 

Massive 

8  "\o     Antigorite 

H4Mg3Si2O9 

Massive 

85  1      Marmolite 

HxMff.SizOo 

Foliated 

852.     Chrysotile   

H4Mg3Si2O9 

Fibrous, 

853.     Picrolite  

H4Mg3Si2O9 

Column. 

854.     Ophicalcite  

H4Mg3Si2O9+MgCaCO3 

Massive 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


245 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

808. 
809. 

Black 
Red 

3 

2 

3 
2-9 

New  York 
Piedmont 

JElec.  purposes 

810. 

Brown 

i-5 

2.9 

California 

8n. 

Grayish 

3-5 

2.9 

North  Carolina 

812. 

Brown 

4 

3 

New  York 

813. 

Bottle  green 

4 

3 

Ural  Mts. 

814. 

Gray 

6-5 

3-5 

Michigan 

815. 

Green 

6-5 

3-5 

Switzerland 

816. 

Green 

6-5 

3 

Belgium 

817. 

Green 

6-5 

3 

Rhode  Island 

818. 

Gray 

6 

3 

Luxembourg 

819. 

Gray 

5-5 

3 

Pyrenees  Mts. 

820. 

Gray 

5,-  5 

3 

New  England 

821. 

Green 

2 

2.6 

Pennsylvania 

822. 

White 

2 

2.6 

Ural  Mts. 

823. 

Red 

2 

2.6 

Southern  Urals 

824. 

Reddish 

Sweden 

19*^1 

825. 

Green 

2 

2.6 

Zermatt 

826. 
827. 

Reddish  violet 
Green 

2 
2 

2.6 
2.6 

Pennsylvania 
Pennsylvania 

Rock  forming 

828. 

Green 

I 

2.7 

North  Carolina 

829. 

Green 

2-5 

2.9 

Massachusetts 

830. 

Green 

2-5 

2.7 

Italy 

831. 

Green 

2.8 

Colorado 

^o   • 

832. 

Green 

2 

2.7 

Connecticut 

833. 

Blackish  green 

2-5 

2.8 

Nova  Scotia 

834. 

Green 

2 

2.7 

Hartz 

835. 

Green 

2-5 

2.6 

Finland 

836. 

Green 

*•$ 

2 

Scotland 

837. 

Velvet  black 

2 

2 

Ireland 

838. 

Black 

3 

3 

Bohemia 

839. 

Green 

2-5 

3 

Arkansas 

840. 

Gray 

3 

3 

Chamoson 

841. 

Black 

3 

2.7 

Silesia 

842. 

Green 

i 

3 

Silesia 

843. 

White 

i-5 

2.6 

Upper  Styria 

844. 

Brown 

i-5 

2.7 

Massachusetts 

845. 

Brown 

!•$ 

2-3 

Massachusetts 

.846. 

Green 

2-5 

2-5 

Maine 

847. 

848. 
849. 

YeUow 
Green 

3-5 

5-5 

2.4 

2-5 

Tyrol 
Rhode  Island 

Rock  forming 

850. 

Green 

2-5 

2.6 

Piedmont 

851. 

White 

4-5 

2.4 

New  Jersey 

852. 

White 

2.2 

Canada 

Cloth 

853. 
854. 

Green 
Green 

2 

3 

2-5 
2-5 

Maryland 
Pennsylvania 

>Rock  forming 

246 


GUIDE  TO  MINERAL  COLLECTIONS 

•        COMPREHENSIVE 


Composition 

Form 

VII.    SILICATES  —  continued 
8  <c  ^      Dewevlite 

4MgO-3SiO2-6H2O 
2NiO  •  2MgO  •  3SiO2  •  6H2O 
H2(Ni,Mg)Si04-H20 
H2Mg3(Si03)4 
H2Mg3(Si03)4 
H2Mg3(Si03)4 
H2Mg3(Si03)4 
H4Mg2Si3OIO 
H4Ni2Si3OIO       • 
5MgO-6SiO2-4H2O 
Mg,Al,H,  silicate 
Fe,Mg,K,  silicate 
Fe,K,H,  silicate 
5H20-K20-i2(Fe,Mg)O-Al2O3-i3Si02 

H4ALSi209 
H4Al2Si209 
H4Al2Si209 
(Al203-2Si02) 
(Al203-2Si02) 
(Al203-2Si02) 
(Al2O3-2SiO2) 
(Al2O3-2SiO2) 
(Al2O3-2SiO2) 
H8Al2Si2On-wH2O 
2Al2O3-9SiO2-6H2O 
H2Al2Si40I2-«H20 
H2Al2Si4OI2-wH2O 
H2Al2(Si03)4 
Al2Si05.5H20 
2Al2O3-SiO2-9H2O 
8Al203-3Si02-3oII20 
H4Ca2(Y,Er)2CSi40I7 
CaSi03  •  CaC03  -  CaSO4  -  1  sH2O 
CaO-2UO3-2SiO2-6H2O 
CuSiO3  •  2H2O 
H8Fe2Si3OI2-2H30 
H8Fe2Si3OI2-2H2O 
H8Fe2Si3OI2-2H2O 
H8Fe2Si3OI2-2H2O 
2Fe2O3-4SiO2-7H2O 
Fe,H,  silicate 
2MnSiO3-H2O 
4MnO-3SiO2-3H2O 
FeMgH,  silicate 

Amorph. 
Amorph. 
Amorph. 
Ortho. 
Ortho. 
Ortho. 
Ortho. 
Earthy 
Hexag. 
Amorph. 
Amorph. 
Earthy 
Amorph. 
Amorph. 

Mono. 
Compact 
Compact 
Massive 
Massive 
Massive 
Massive 
Massive 
Massive 
Hexag. 
Amorph. 
Massive 
Massive 
Massive 
Amorph. 
Massive 
Massive 
Ortho. 
Tetrag. 
Ortho. 
Amorph. 
Massive 
Massive 
Massive 
Massive 
Amorph. 
Amorph. 
Foliated 
Massive 
Amorph. 

856      Genthite          

857      Garnierite     

858     Talc            

850      Steatite 

860      French  chalk 

86  1      Rensselaerite 

862      Sepiolite 

86  3      Connarite                .  . 

864      Spadaite 

86  <      Saponite              

866.     Celadonite  
867      Glauconite 

868      Pholidolite  

d.  Kaolins 
869      Kaolinite     

870.    Lithomarge   

871.     Pholerite  

872.    Halloysite  

873.     Pseudosteatite  
8  74      Indianaite 

875.     Smectite  

876      Bole 

877      Bergseife 

878      Newtonite 

879.     Cimolite 

880.     Montmorillonite   .  .  . 

881.     Stolpenite  

882.     Pyrophyllite  

883.    Allophane  

884.     Collyrite  

885.     Schrotterite  

886      Cenosite 

887      Thaumasite 

888.     Uranophane  
889.     Chrysocolla  

890.     Chloropal  
891.    Nontronite  

892.     Pinguite   

893.     Graminite  

894.    Hoef  erite  

895.     Hisingerite 

896.     Bementite 

897.     Caryopilite 

898.     Neotocite           ...    . 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


247 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

855. 
856. 

Whitish 
Green 

2 

3 

2 
2 

Maryland 
Texas 

>Rock  forming 

8^7 

Green 

2  .  3 

North  Carolina 

Nickel 

uo  /  • 
858. 

Green 

i 

•  o 

2.7 

Vermont 

Lubricants 

859. 

Gray 

i 

2-5 

Virginia 

Soapstone 

860. 

White 

i 

2.5 

Virginia 

861. 

White 

i 

2-5 

New  York 

^Lubricants 

862. 

White 

2 

2 

Asia  Minor 

J 

863. 

Green 

2-5 

2 

Saxony 

Nickel  f 

864. 

Reddish 

2-5 

Italy 

Magnesium 

865. 
866. 

White 
Green 

I 
I 

2 

Scotland 
Verona 

>Rock  forming 

867. 

Green 

2 

2 

New  Jersey 

Fertilizer 

868. 

Yellow 

2 

2 

Sweden 

Rock  forming 

869. 

White 

2 

2.6 

Delaware 

870. 

White 

2 

2 

Germany 

871. 

White 

2 

2 

France 

872. 

White 

I 

2 

Illinois 

873- 

Green 

2 

2 

Illinois 

874. 

White 

2 

2 

Indiana 

875. 

Greenish 

2 

2 

France 

876. 

Brown 

2 

2 

Illinois 

877- 

Brown 

2 

2 

California 

878. 

White 

I 

2 

Arkansas 

879. 

White 

I 

2 

Argentina 

880. 

White 

I 

2 

St.  Jean  Ode-Cole 

881. 

White 

I 

2 

France 

882. 
883. 
884. 
885. 

White 
Blue 
White 
Green 

I 

3 

i 

3 

2.8 
1.8 
2 
1.9 

North  Carolina 
Pennsylvania 
Pyrenees 
Alabama 

Brick,   fire  clay, 
pottery,  and 
rock  forming 

886. 

Brown 

5 

3 

Norway 

887. 

White 

3-5 

1.8 

New  Jersey 

888. 

Yellow 

3-5 

1.8 

North  Carolina 

889. 

Green 

2 

2 

New  Jersey 

890. 

Yellow 

2-5 

i-7 

Pennsylvania 

891. 

Yellow 

2-5 

i.7 

France 

892. 

Green 

I 

i-7 

Saxony 

893- 

Green 

I 

i-7 

Menzenberg 

894. 

Green 

I 

2-3 

Bohemia 

895- 

Black 

3 

2-5 

Sweden 

896. 

Yellow 

i 

2.9 

New  Jersey 

897- 

Brown 

3 

2.8 

Sweden 

898. 

Black 

3 

2.6 

Sweden 

248 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

Vila.      TlTANATES 

899.    Titanite 

CaTiSiO5 

IVIono 

900.     Sphene     .  .    . 

CaTiSiOs 

M^ono 

901.    Ligurite   

CaTiSiOs 

Mono 

902.     Spinthere  

CaTiSiOg 

Mono 

903.    Lederite  
904.    Titanomorphite  

CaTiSiOs 
CaTiSiOs 

Mono. 
Mono. 

905.     Greenovite  
906.     Grothite 

CaTiSi05 
CaTiSiOs 

Mono. 
M^ono 

907.     Keilhauite 

i5CaSiTiOs-  (Al,Fe,Y)2(Si  Ti)Os 

]VJono 

908.     Guarinite   

CaTiSiOs 

Ortho 

909.     Tscheffkinite  

iSCaSiTiOs-  (Al  Fe  Y)a(Si  Ti)Os 

JVIassive 

910.     Astrophyllite   

(Na  K)4(Fe.Mn)4Ti(SiO4)4 

Ortho 

911.    Johnstrupite  

Ce,Ca,Na,Ti,Fe,  silicate 

Mono. 

912.     Mosandrite  

Ce,Ca,Na,Ti,Fe,  silicate 

Prism. 

913.    Rinkite 

Ce  Ca  Na  Ti  Fe  silicate 

Mono 

914.    Neptunite 

Ce  Ca  Na  Ti  Fe  silicate 

Mono 

915.     Perovskite  
916.     Knopite 

CaTi03 
CaTiO3,  much  Ce 

Regular 
Regular 

917.     Dysanalyte  
918.     Geikielite  

6(Ca,Fe)TiO3  •  (Ca,Fe)Nb2O6 
MgTiO3 

Regular 
Missive 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


249 


No 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

899. 

Brown 

5 

3 

Massachusetts 

900. 

Brown 

5 

3 

Massachusetts 

901. 

Yellow 

5 

3 

Massachusetts 

902. 

Green 

5 

3 

Massachusetts 

9°3- 

Brown 

5 

3 

Massachusetts 

904. 

White 

5 

3 

Massachusetts 

90S- 

Red 

5 

3 

Massachusetts 

906. 

Brown 

6 

3 

Dresden 

907. 

Black 

6-5 

3-5 

Norway 

908. 

Yellow 

6 

3 

Mt.  Somma 

Rock  forming 

909. 

Black 

5 

4-5 

Ilmen  Mts. 

910. 

Yellow 

3 

3 

Colorado 

on. 

Green 

Norway 

V        • 

912. 

Brown 

4 

2.9 

Norway 

•  > 

9*3- 

Brown 

5 

3 

Greenland 

'• 

914. 

Black 

5 

3 

South  Greenland 

9*5- 

Yellow 

5-5 

4 

New  York 

916. 

Black 

Sweden 

• 

917. 

Black 

5 

4 

Baden 

5 

918. 

Black 

6 

4 

Ceylon 

250 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

VIII.    NIOBATES,  TANTA- 

LATES 

919.     Pyrochlore  
920.    Hatchettolite  

(G,Nb,Ti,Th,Ce,Ca,Fe,U,Mg,NaF,)  •  O 
(G,Nb,Ti,Th,Ce,Ca,Fe,U,Mg,NaF  )  -O 

Regular 
Regular 

921.    Microlite  

Ca2Ta2O7 

Regular 

922.     Pyrrhite  

Ca2Ta2O7+Nb,Ti,Ce,Na 

Regular 

923.     Fergusonite  

(Y,Er,Ce)(Nb,Ta)O4 

Tetrag 

924.     Sipylite  

Er  Nb  O4 

Tetrag. 

925.     Columbite-tantalite  .  . 
926.    Tapiolite 

(Fe,Mn)(Nb,Ta)206 
Fe(Ta,Nb)2O6 

Ortho. 
Regular 

927.    Yttro  tan  tali  te  .    ... 

W,Sn,Y,Er,Ce,U,Fe,Ca,H,Nb,  tantalate 

Ortho. 

928.     Samarskite  

G,Sn,W,U,Ce,Di,La,Y,Er,Fe,Mn,Ca, 

Ortho. 

929.    Annerodite  

H,Nb,  tantalate 
Pyroniobate  of  U,Y 

Ortho. 

930.    Hielmite 

Y  Fe  Mn  Ca  Sn  Nb  tantalate 

Ortho 

931.    Aeschynite 

Ce  Th,Fe,Ca,Nb,  titanate 

Ortho. 

032.    Polvmiffnite 

Ce,La,Di,Fe,Ca,Nb,Zn,Sn,Th,  titanate 

Ortho. 

933.    Euxenite 

Y,Er,Ce,U,H,Nb,  titnate 

Ortho. 

934.    Polycrase  

G,Nb,Y,Er,Ce,U,Fe,Ta,H2O,  titanate 

Ortho. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


251 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

919. 

Brown 

5 

4 

Norway 

920. 

Brown 

4-7 

North  Carolina 

921. 

Yellow 

5-5 

5 

Massachusetts 

922. 

Yellow 

Urals 

923- 

Black 

5-5 

5-8 

Carolinas 

924. 

Black 

6 

4-8 

Virginia 

925. 

Iron  black 

6 

5 

N.  England  states 

926. 

Black 

6 

7 

Finland 

927. 

Black 

5 

5-5 

Sweden 

Rock  forming 

928. 

Black 

5 

5-6 

North  Carolina 

929. 

Black 

6 

5-7 

Norway 

930. 

Black 

5 

5-8 

Sweden 

931. 

Black 

5 

4-9 

Ilmen  Mts. 

932. 

Black 

6 

4-7 

Norway 

933- 

Black 

6-5 

4-9 

Norway 

934- 

Black 

5 

4-9 

South  Carolina 

252 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

IX.    PHOSPHATES,   ARSE- 
NATES,  ETC. 
i.  Anhydrous 
935.    Xenotime  

YPO4 

Tetrae 

936.     Monazite  

(Ce,La,Di)PO4 

Mono 

937.     Berzeliite  

(CaMgMn)3As2Og 

Regular 

938.     Monimolite 

(Pb  Fe  Ca)3Sb2O8 

939.     Carminite 

Pb3As2O8-  ioFeAsO4 

Ortho 

940.     Pucherite 

BiVO4 

Ortho 

941.     Triphylite 

LiFePO4 

Ortho 

942.     Lithiophilite  .  .  . 

LiMnPO4 

Ortho 

943  .     Natrophilite  

NaMnPO4 

944.     Beryllonite  

NaBePO4 

Ortho 

945.     Apatite  

(CaF,Cl)Ca4(PO4)3 

Hexajj 

946.     Moroxite  

(CaF,Cl)Ca4(PO4)3 

Hexajr 

947.    Lasurapatite  

(CaF,Cl)Ca4(PO4)3 

Hexag 

948.     Francolite 

(CaF  Cl)Ca4(PO4)3 

949.     Manganapatite  

(CaF,  Cl)  Ca4  (PO4)3  +  Mn 

Hexag. 

950.     Phosphorite  
951.     Eupyrchroite  
952.     Staffelite  .  .  .    . 

(CaF,Cl)Ca4(P04)3 
(CaF,Cl)Ca4(P04)3 
(CaF,Cl)Ca4(PO4), 

Concret. 
Concret. 
Concret 

953.     Earthy  apatite;  osteo- 
lite  

Altered  apatite 

Earthy 

954.     Pyromorphite  

(PbCl)Pb4(PO4)3 

Hexag. 

955.     Polysphaerite  
956.     Miesite  

(PbCl)Pb4(C04)3+Ca 
(PbCl)Pb4(PO4)3+Ca 

Hexag. 
Hexag. 

957.     Nussierite 

Impure  polysphaerite 

958.     Mimetite 

(PbCl)Pb4(AsO4)3 

Hexag 

CKQ.     Campylite 

(PbCl)Pb4(AsO4)3+P 

Hexag 

960.     Endlichite  

PbsCl(As  VO4)3 

Hexag. 

96  1  .     Vanadinite  

(PbCl)Pb4(VO4)3 

Hexag. 

962.     Hedyphane  

(Pb,Ca,Ce)4(AsO4)3 

Mono. 

963.     Svabite  

Ca(F,Cl,OH)  Ca4(AsO4)3 

Hexag. 

964.    Wagnerite  

(MgF)MgPO4 

Mono. 

965.     Spodiosite  
966.     Triplite 

(CaF)CaP04 
(Fe,Mn)PO4 

Mono. 
Mono. 

967.     Talktriplite  
968.     Triploidite   .         ... 

(Fe,Mn,Ca,Mg)P04 
(Fe3,Mn,OH)PO4 

Mono. 
Mono. 

969.     Adelite  

(MgOH)CaAsO4 

Mono. 

970.     Tilasite  

(Mg,FOH)CaAsO4 

Mono. 

971.     Sarkinite 

(MnOH)MnAsO4 

Mono. 

972.     Herderite 

(CaF)BePO4 

Mono. 

973.     Hamlinite          .    . 

Al3Sr(OH)7P2O7 

Hexag. 

974.     Durangite  
975.     Amblygonite  

Na(AlF)AsO4 
Li(AlF)PO4 

Mono. 
Triclinic 

2.  Basic 
976.     Olivenite 

Cu3As2O8-Cu(OH)2 

Ortho. 

977.     Libethenite  

Cu3P208-Cu(OH), 

Ortho. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


253 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

935- 

Brown 

4 

4 

G:orgia 

936. 

Red 

5 

4-9 

Connecticut 

937- 

Yellow 

5 

4 

Sweden 

0^8 

Brown 

6   e 

Pajsberg 

VO0> 

939- 
940. 

Red 
Brown 

2-5 

4 

*  0 

4 
6 

Nassau 
Saxony 

Rock  forming 

941. 

Gray 

4-5 

3 

Massachusetts 

942. 

Yellow 

4-5 

3 

Connecticut 

943- 

Wine  yellow 

4-5 

3 

Connecticut 

944. 

Colorless 

5-5 

2.8 

Maine 

945- 

Green 

5 

3 

Maine 

946. 

Blue 

5 

3 

Arendal 

947- 

Sky  blue 

5 

3 

Siberia 

948. 

Grayish  green 

5 

3 

England  . 

949- 

Green 

5 

3 

Delaware 

Phosphorus 

95°- 

Green 

5 

3 

Spain 

951- 

Gray 

4-5 

3 

New  York 

952. 

Yellow 

4 

3 

Staffel 

953- 

Green 

3-5 

6-5 

New  York 

954- 

Green 

3-5 

6-5 

Pennsylvania 

955- 

Brown 

5-8 

Cornwall 

956. 

Brown 



5 

Bohemia 

957- 

Yellow 



5 

France 

958. 

Yellow 

3-5 

7 

Pennsylvania 

Lead 

959- 

Brown 

7 

Cumberland 

960. 

Brown 

2.7 

6.6 

Arizona 

961. 

Red 

2.7 

6.6 

Arizona 

962. 

White 

4 

5 

Sweden 

963- 

Colorless 

5 

3-5 

Sweden 

} 

964. 

White 

5 

3 

Austria 

>Rock  forming 

965- 

Ash  gray 

5 

2.9 

Sweden 

/ 

966. 

Gray 

4 

3 

Connecticut 

967. 
968. 

Gray 
Brown 

4 
4-5 

3-6 

Horrsjoberg 
Connecticut 

Phosphorus 

969. 

Yellow 

5 

3-7 

Sweden 

970. 

Yellow 

5 

3-7 

Langban 

Rock  forming 

971. 

Red 

4 

4 

Sweden 

) 

972. 

White 

5 

2-9 

Maine 

^Manganese 

973- 

Colorless 

4-5 

3 

Maine 

j 

974- 

Orange  red 

3-9 

Mexico 

Arsenic 

975- 

White 

..£., 

3 

Maine 

Phosphorus 

976. 
977- 

Green 
Green 

3 
4 

4 
3-6 

Utah 
Cornwall 

>Copper 

254 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

IX.    PHOSPHATES,  ARSE- 
NATES  —  continued 
978.    Tarbuttite 

Zn3P208-Zn(OH)2 
Zn3As2O8-Zn(OH)2 
(Pb,Zn)a(OHJVQ4 
PbZnCuV2O8 
PbV206 
(Cu,Ca)3V208-(Cu,Ca)(OH)2 
(Pb,Fe,Mn)3V208-H20 
(Pb,Cu)4(OH)2V208-H2O 
(Pb,Cu)4(OH)2V208-H20 
Cu3As2O8-3Cu(OH)2 
Cu3As2O8-2Cu(OH)2 
Cu3P2O8-2Cu(OH)2 
Cu3P208.3Cu(OH)2 
Mn3As2O8-3Mn(OH)2 
Mn3As2O8-3Mn(OH)2+H2O 
FeP04-Fe(OH)3 
(Fe,Mn)Al2(OH)P04 
Ca3P203-2Al(OH)2 
Ca3Al(P04)3-Al(OH)3 
Ca3Fe(As04)3.3Fe(OH)3 
Mn3As2O8-4Mn(OH)2 
2  (Al,Mn)  AsO4  •  5Mn(OH)2 
MnAsO<-2Mn(OH)2 
(Al,Mn)As04.4Mn(OH)2 
Mn,Ca,Ce,Li,Ca,Mg,  arsenate 
Sb,Fe,Mn,Pb,Ca,Mg,HSP,  arsenate 
ioMnO-(Sb,As)2O5 
H2Bi3AsO8 

(NH4)MgPO4-6H20 
Ca3P2O8-H2O 
Mg2P2O7  •  4  (Ca3P2O8  +  Ca2P2O7) 
Zn3P208-H20 
(Mn,Ca,Fe,Na2)3(PO4)2-fH2O 
Fe,Mn,Ca,Na,Li,  hydrous  phosphate 
(Ca,Co,Mg)3As208-2H2O 
Ca2MnAs2O8-2H2O 
Ca2MnP2O8-2H2O 
(Ca,Fe)3P208-2^H20 
Mn3P208-3H20 
(Ca,Mg)3As208-6H20 
Cu3As2O8-5H2O 
Fe3P2O8-8H2O 
Fe3As2O8-8H2O 
Mg3P2O8-8H2O 
Mg3As208-8H2O 
Co3As2O8-8H2O 

Triclinic 
Ortho. 
Ortho. 
Massive 
Massive 
Ortho. 
Mono. 
Coatings 
Coatings 
Mono. 
Concent. 
Mono. 
Massive 
Mono. 
Mono. 
Ortho. 
Mono. 
Mono. 
Mono. 
Tetrag. 
Mono. 
Mono. 
Ortho. 
Hexag. 
Ortho. 
Hexag. 
Ortho. 
Mono. 

Ortho. 
Amor. 
Massive 
Ortho. 
Hexag. 
Mono. 
Triclinic 
Triclinic 
Triclinic 
Triclinic 
Ortho. 
Ortho. 
Ortho. 
Mono. 
Mono. 
Mono. 
Mono. 
Mono. 

979.     Adamite  

980.     Descloizite  

98  1  .     Eusynchite  

982.     Dechenite  

983.     Calciovolborthite  .  .  .  . 
984.     Brackebuschite  

985.     Psittacinite 

986.     Mottramite  
987.     Clinoclasite  
988.     Erinite   . 

989.     Dihydrite.  ... 

990.     Pseudomalachite  .  . 

991.     Chondrarsenite  

992.     Xantharsenite  

993.     Dufrenite  

994.    Lazulite  

995.     Tavistockite  

996.     Cirrolite 

997.    Arseniosiderite  
998.    Allacite  .  . 

999.     Synadelphite  
1000.     Flinkite  

1001.     Hematolite  

1002.     Retzian  

1003.     Arseniopleite  

1004.     Manganostibiite  ..... 

1005.     Atelestite 

3.  Normal  Hydrous 
1006.     Struvite 

1007.     Collophanite  
1008.     Pyrophosphorite 

1009.     Hopeite  

1010.     Dickinsonite  

ion.     Fillowite  

1012.     Roselite  

1013.     Brandite 

1014.     Fairfieldite  
1015.     Messelite 

1016.     Reddingite 
1017.     Picropharmacolite  
1018.     Trichalcite  

1019.     Vivianite 

1  020.     Symplesite             .    .  . 

1021.     Bobierrite  

1022.     Hoernesite  

1023.     Erythrite  

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


255 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

978. 

Brown 

3-5 

4 

Rhodesia 

\7inr 

979- 

Yellow 

3-5 

4 

Chile 

fZ^lIlC 

980. 

Red 

3-5 

5-9 

Arizona 

Lead 

981. 

Red 

3 

5-5 

Baden 

982. 

Red 

3 

5-6 

Bavaria 

983- 

084. 

Green 
Black 

3 

3-8 

Thuringa 
Argentina 

Vanadium 

V    T" 

08  1C 

Green 

Montana 

V°Jt 

086 

Black 

England 

yuw. 
987. 

Green 

2-5 

4 

Cornwall 

988. 
989. 

Green 
Green 

4 
4-5 

4 
4 

Cornwall 
Urals 

Copper 

990. 

Dark  green 

4 

3 

Rheinbreitenbach 

991. 

002 

Yellow 
Yellow 

3 

Sweden 
Sweden 

^Manganese 

yy  " 
993- 

Green 

3-5 

3 

New  York 

Phosphorus 

994. 

Blue 

5 

3 

North  Carolina 

Gems 

QQC. 

White 

Devonshire 

i 

yyo 
996. 

Yellow 

5 

3 

Sweden 

>Phosphorus 

997- 

Brown 

i 

3 

France 

Arsenic 

998. 

Red 

4 

3 

Sweden 

999. 

IOOO. 

Black 
Brown 

4 
4 

3-8 

Sweden 
Sweden 

Manganese 

IOOI. 

Red 

3-5 

3 

Nordmark 

1002. 

Brown 

4 

4 

Nordmark 

Arsenic 

IOO3 

Red 

Sweden 

Arsenic 

iv-"~'G' 

IOO4 

Black 

. 

Sweden 

Manganese 

J.  UU^.. 

1005. 

Yellow 

3 

6 

Saxony 

Bismuth 

1006. 

White 

2 

1.6 

Victoria 

Lead 

1007. 
1008. 

Colorless 
White 

2 

3 

2 
2 

Sombrero  Islands 
West  Indies 

^Phosphorus 

1009. 

White 

2-5 

2-7 

Altenberg 

Zinc 

IOIO. 
IOII. 

Green 
Yellow 

3-5 
4 

3 
3 

Connecticut 
Connecticut 

>Phosphorus 

IOI2. 
1013. 

Red 
Colorless 

3 

5 

3-5 
3-6 

Saxony 
Sweden 

jArsenic 

IOI4. 

White 

3-5 

3 

Connecticut 

) 

1015. 

Colorless 

3-5 

Hesse 

^Phosphorus 

1016. 

White 

3 

3 

Connecticut 

J 

IOI7. 

White 

Missouri 

Arsenic 

xvsj.  i  • 

1018. 

Green 

2 

Turginsk 

Copper 

1019. 

Colorless 

i-5 

2-5 

New  Jersey 

Phosphorus 

IO2O. 

Indigo 

2-5 

2.9 

Carinthia 

Arsenic 

IO2I. 

Colorless 

Norway 

Phosphorus 

IO22. 
1023. 

White 
Red 

i 
i-5 

2.4 

2-9 

Hungary 
California 

>  Arsenic 

256 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

IX.    PHOSPHATES,  ARSE- 
NATES  —  continued 
1024.     Annabergite  
1025.     Cabrerite   

Ni3As2O8-8H2O 

(Ni,Mg)3As2O8  •  8H2O 

Mono. 
Miono 

1026.     Kottigite  

Zn3As2O8-8H2O 

M^ono 

1027.    Rhabdophanite  

(  Y,Er)2O3  •  (La,Di)2O3  •  P2O3  •  H2O 

M!ono 

1028.     Churchite  

Ce2O3  •  CaO  •  PD2O5H2O 

Mono 

1029.     Scorodite  

FeAsO4-2H2O 

Ortho. 

1030      Strcngite 

FePO4-2H2O 

Ortho 

1031.     Phosphosiderite  
1032.     Barrandite  
IO33      Variscite 

2FeP04.3£H20 
(Al,Fe)P04-2H2O 
A1PO4-2H2O 

Ortho. 
Ortho. 
Ortho 

1034      Callanite 

A1PO4-2^H2O 

Ortho 

1035      Zepharovichite  .... 

A1PO4-3H2O 

Ortho 

1036.     Koninckite  

FePO4-3H2O 

Ortho. 

4.  Acid  Hydrous 
1037.     Pharmacolite     ...    . 

HCaAsO4-2H2O 

Mono. 

1038      Haidingerite  

HCaAsO4-H2O 

Ortho. 

1039.    Wapplerite  

HCaAsO4-3^H2O 

Mono. 

1040.     Brushite  

HCaPO4-2H2O 

Mono. 

1041.     Martini  te  

H2Cas(PO4)4^H2O 

Hexag. 

1042.     Newberyite  
1042^.  Stercorite  

HMgP04-3H20 
HNa(NH4)PO4-4H2O 

Ortho. 
Mono. 

1043      Hureauli  tc 

H2Mns(PO4)4-4H2O 

Mono. 

1044      Forbesite 

H2(Ni,Co)2As2O8  •  8H2O 

Mono. 

5.  Basic  Hydrous 
1045      Isoclasite 

Ca3P2O8  •  Ca(OH)2  •  4H2O 

Mono. 

1046.    Hemafibrite  
1047      Euchroite 

Mn3As2O8  •  3Mn(OH)2  •  2H2O 
CUiAszOg  •  Cu(OH)2  •  6H2O 

Ortho. 
Ortho. 

1048      Conichalcite  

(Cu,Ca)3As2O8  •  (Cu,Ca)  (OH)2  -  £H2O 

Ortho. 

1049.     Bayldonite     

(Pb,Cu)3As2O8  •  (Pb,Cu)  (OH)2  -  H2O 

Mono. 

1050.     Tagilite 
1051.    Leucochalcite  

Cu3P208Cu(OH)-2H20 
Cu3As2O8  •  Cu(OH)2  •  2H2O 

Mono. 
Mono. 

i  o  "5  2      Volb  orthi  t6 

(Cu,Ca,Ba)3(OH)3VO4-6H2O 

Ortho. 

1053      Cornwallite 

Cu3  As2O8  •  2  Cu  (OH)2  •  H2O 

Ortho. 

1054     Tyrolite 

Cu3As2O8  •  2Cu(OH)2  •  7H2O 

Ortho. 

1055      Chalcophyllite 

7CuO  •  As2O5i4H2O 

Hexag. 

1056      Veszelyite  ...       ... 

7  (Zn,Cus)  (P,  AS)2OS  •  9H2O 

Mono. 

1057.    Wavellite   

4A1PO4  •  2  A1(OH)3  •  9H2O 

Ortho. 

1058.     Fischerite  

A1PO4-A1(OH)3-2|H2O 

Ortho. 

1059.     Peganite  

A1(PO4)  •  A1(OH)3  •  i^H2O 

Orhto. 

1060.     Turquois  

A1PO4-A1(OH)3-H2O 

Amorph. 

1  06  1      Wardite 

2A12O3-P2OS-4H2O 

Crusting 

1062      Sphaerite 

4A1PO4-6A1(OH)3 

Ortho. 

1063.    Liskeardite  

(  Al,Fe)  AsO4  •  2  (Al,Fe)  (OH)3  •  5H2O 

Ortho. 

1064.     Evansite  

2A1PO4  -4A1(OH)3  -  1  2H2O 

Ortho. 

1065.     Coeruleolactite  
1066      Augclitc 

3Al2032PaOs.ioH20 
2A12O3-PA-3H2O 

Mono. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


257 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

1024. 

Green 

2 

Nevada 

1 

1025. 

Green 

2 

2.9 

Spain 

iArsenic 

IO26. 

Red 

2-5 

3 

Schneeberg 

J 

1027. 

Brown 

3-5 

3-9 

Cornwall 

Rare  elements 

1028. 

Smoke  gray 

3-5 

3 

Cornwall 

Cerium 

IO2Q. 

Green 

3-5 

3 

Utah 

Arsenic 

1030. 

Red 

3 

2.8 

Virginia 

1031. 

Red 

3-7 

2.7 

Germany 

1032. 

Gray 

4-5 

2-5 

Bohemia 

1033. 

Green 

4 

Utah 

Phosphorus 

1034. 

Green 

3-5 

2-5 

Lockmariaquer 

1035. 

White 

5-5 

2-3 

Bohemia 

1036. 

Yellow 

3-5 

2-3 

Belgium 

1037. 

White 

2 

2.6 

Joachimsthal 

Arsenic 

1038. 
1039. 

White 
Colorless 

!-5 
2 

2 
2 

Joachimsthal 
Joachimsthal 

Rock  forming 
Arsenic 

1040. 

Colorless 

2 

2 

Caribbean  Sea 

1041. 

Yellowish 

2.8 

Western  India 

1042. 

White 

3 

2 

Victoria 

Phosphorus 

1042!. 

White 

2 

1.6 

Peru 

1043. 

Yellow 

5 

3 

Connecticut 

1044. 

White 

2.5 

3 

Atacama 

Arsenic 

1045. 

White 

I 

2.9 

Joachimsthal 

Calcium 

1046. 

Red 

•3 

3-5 

Sweden 

Manganese 

1047. 

Green 

3-5 

3 

Hungary 

1048.  . 

Green 

4 

4 

Utah 

1049- 

Green 

4 

5 

Cornwall 

1050. 

Green 

3 

4 

Urals 

1051. 

White 

Germany 

1052. 

Green 

3 

3 

Urals 

Copper 

I°53- 

Green 

4 

4 

Cornwall 

1054. 

Green 

i 

3 

Utah 

JOSS- 

Green 

2 

2 

Utah 

1056. 

Blue 

3-5 

3-5 

Banat 

1057. 

White 

3 

2 

Saxony 

] 

1058. 

Green 

5 

2-4 

Urals 

I  Phosphorus 

1059. 

Green 

3 

2.4 

Saxony 

J 

1060. 

Green 

6 

2.6 

New  Mexico 

Gems 

1061. 

Green 

5 

2.7 

Utah 

Phosphorus 

1062. 

Gray 

4 

2-5 

Bohemia 

1063. 

White 

Cornwall 

1064. 

Colorless 

4 

1.9 

Hungary 

Aluminum 

io6s. 

White 

Pennsylvania 

j* 
1066. 

Colorless 



2.7 

Sweden 

258 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

IX.    PHOSPHATES,  ARSE- 
NATES  —  continued 
1067.     Berlinite  

2A12-O32P2OS-H20 
4A1203-3P20S-3H20 
P2Os-Al2-03,MnO,CaO,H20,  etc. 
6FeAsO4  •  2Fe(OH)3  -  1  2H2O 
2Fe3P2O8Fe(OH)2  •  8H2O 
FeP04Fe(OH)3-4iH20 
2FeP04-Fe(OH)3.2iH2O 
2AlP04-2Fe(OH)2.2H20 
2AlPO4-2Fe(OH)2-2H2O 
Ca3Fe2(As04)4  •  2FeO(OH)  -  5H2O 
Ca3Fe2(P04)4  -  Fe(OH)3  •  8H2O 
Ca3Fe2(PO4)4  •  1  2Fe(OH)3  -  6H2O 
4FeP208  •  Fe2OF2(OH)2  -  36H2O 
Cu6Al(AsO4)s  •  3CuAl(OH)s  •  2oH2O 
Cu2(FeO)2As208-3H20 
Fe,Cu,Ca,Al,H,  phosphate 
CuO  •  3Fe2O3  •  2P2OS  -  8H2O 
5Fe203-P2Os-SH20 
Fe,Zn,Ca,Mg,Al,H,  phosphate 
Ca3AlIOP2O23-9H2O 
PbO  •  2  A12O3  •  P  A  •  9H2O 
Cu(U02)2P208-8H20 
Cu(U02)2As208-8H2O 
Ca(U02)2P208-8H20 
Ca(U02)2As208-8H20 
Ba(U02)2P208-8H20 
(UO2)3P2O8-6H2O 
(U02)3As208-i2H2O' 
BiIO(U02)3(OH)24(As04)4 
2BiAsO4-3Bi(OH)3 
2oCuO  •  Bi2O3  •  5  AsA  •  2  2HaO 

Ca2Sb2O7 
Pb3Sb208-4H2O 
CaSb2O4 
PbClSbO. 
Pb4As2O7-2PbCl2 
Pb4Sb207-2PbCla 
CuO,AS2O3 
2FeO-Sb2Os 
FeO-Sb2Os-sFeO-TiOa 
5CaO-2Ti02-3Sb2Os 
Pb,Ca,Ti,  antimonate 
Cu,Hg,Fe,S,  antimonate 

Massive 
Compact 
Massive 
Regular 
Mono. 
Tufts 
Mono. 
Ortho. 
Ortho. 
Ortho. 
Mono. 
Mono. 
Mono. 
Mono. 
Mono. 
Mono. 
Triclinic 
Triclinic 
Amorph. 
Tetrag. 
Hexag. 
Tetrag. 
Tetrag. 
Ortho. 
Ortho. 
Ortho. 
Powder 
Mono. 
Triclinic 
Triclinic 

1068     Trolleite 

1069.     Attacolite 

1070.     Pharmacosiderite  .  .  .  . 
1071.    Ludlamite        

1072.     Cacoxenite  

1073.     Beraunite  

1074.     Childrenite  
1075.    Eosphorite  

1076      Masapilite 

1077      Calcioferrite 

1078      Borickite 

1079.     Richellite       .  .    .  . 

1080.    Liroconite  

1081.     Chenevixite   

1082.    Henwoodite  

1083.     Chalcosiderite  

1084.     Andrewsi  te  

1085      Kehoeite 

1086      Goyazite 

1087.     Plumbogummite  
1088.    Torbernite  
1089.    Zeunerite   

1090.     Autunite  

1091.     Uranospinite  

10921    TJranocircite 

1  093  .     Phosphuranylite 
1094     Trogerite 

1095.    Walpurgite  

1096.     Rhagite  

1097     M!ixite 

6.  Antimonates 
1098.    Atopite  

Regular 
Amorph. 
Tetrag. 
Ortho. 
Tetrag. 
Ortho. 
Tetrag. 
Ortho. 
Ortho. 
Regular 
Regular 
Earthy 

1099      Bindheimite 

1  1  o  i      Nadorite 

1102.     Ecdemite       

1103.     Ochrolite     

1  103(1.  Trippkeite  

1104     Tripuhyite 

1105      Derbylite 

1106.    Lewisite 
1107.    Mauzeliite     

1108.    Ammiolite  

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


259 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

1067. 

Colorless 

6 

2.6 

Germany 

} 

1068. 

Green 

5-5 

3 

Sweden 

^Phosphorus 

/: 

Salmon  red 

J 

1070. 

Green 

2-5 

2-9 

Utah 

/ 

Arsenic 

1071. 

Green 

3 

3 

Cornwall 

1072. 

Yellow 

3 

3 

Pennsylvania 

IO73 

Brown 

Bohemia 

Phosphorus 

1074. 

White 

4-5 

3 

Maine 

I°75- 

Pink 

4-5 

3 

Connecticut 

1076. 

Black 

4-5 

3-5 

Mexico 

Arsenic 

1077. 

Yellow 

2 

2 

Bavaria 

1078. 

Brown 

3-5 

2.6 

Bohemia 

Phosphorus 

1079. 

Yellow 

2 

2 

Belgium 

I080. 

1081. 

Blue 
Green 

2 

3-5 

2.8 

3-9 

Cornwall 
Utah 

Arsenic 

1082. 

Blue' 

4 

2.6 

Cornwall 

1083. 

Green 

4 

3 

Cornwall 

1084. 

Bluish  green 

4 

3 

Cornwall 

Phosphorus 

1085. 

2  -3 

South  Dakota 

1086. 

White 

5 

3 

Brazil 

1087. 

Yellowish 

4 

4 

Brittany 

Lead 

1088. 

Green 

2 

3 

Cornwall 

1089. 

Green 

2 

3 

Cornwall 

1090. 

Yellow 

2 

3 

North  Carolina 

1091. 

Green 

2 

3 

Saxony 

Uranium 

1092. 

Green 

3-5 

Voigtland 

IOCH. 

Yellow 

North  Carolina 

vo 

1094. 

Yellow 

3 

Saxony 

1095. 

1096. 

Yellow 
Yellow 

3-5 

5 

5-7 
6 

Saxony 
Saxony 

>Bismuth 

1097. 

Green 

3-5 

5 

Utah 

Copper 

1098. 

Yellow 

5-5 

5 

Sweden 

Antimony 

1099. 

Gray 

4 

4 

Arkansas 

Lead 

1  100. 

Yellow 

5-5 

4-7 

Piedmont 

Antimony 

IIOI. 

Yellow 

3-5 

7      ' 

Algeria 

1 

IIO2. 

Yellow 

2-5 

7 

Sweden 

Lead 

IIO3. 

Yellow 

Chile 

j 

•  XWO 

1103*1. 

Bluish  green 

Brazil 

Copper 

1104. 

Greenish  yellow 

5 

Brazil 

Antimony 

1105. 

Black 

5 

4 

Brazil 

Titanium 

1106. 

Yellow 

4 

Brazil 

\ 

1107. 

Brown 

"(3 

5 

Sweden 

^Antimony 

1108. 

Scarlet 

Chile 

J 

/ 

260 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

IX.    PHOSPHATES,  ARSE- 
NATES  —  continued 

7.  Mixed  Phosphates  . 
1109.     Diadochite       

2  Fe2O3  •  2  SO3  •  P2Oi  •  1  2H2O 

Mono. 

i  no.     Destinezite  

2Fe2O3  •  2SO3  •  P2OS  •  1  2H2O 

Earthy 

1  1  1  1  .    Pitticite  

Fe,S,  arsenate 

Massive 

ii  12.     Svanbergite  

Ca,Al,S,  phosphate 

Hexag. 

1  1  13      Beudantite 

Fe,Pb,S  AS,  phosphate 

Hexag. 

1114.    Lindackerite  
1115      Liinebergite 

3NiO  •  6CuO  -  S032  As20s  -  7H2O 
3MgO  •  B2O3  •  P2OS  •  8H2O 

Ortho. 
Earthy 

1116.    Lossenite           

2PbSO4  •  3  (FeOH)3As2O8  •  1  2H2O 

Ortho. 

8.  Nitrates,  etc. 
1117.     Soda  niter  
1118.     Niter                

NaNO3 
KNO3 

Hexag. 
Ortho. 

1119.    Nitrocalcite   

Ca(NO3)2-nH2O 

1  1  20.    Nitromagnesite  

Mg(NO3)2-nH2O 

n  2  1  .     Nitrobarite  

Ba(NO3)2 

Regular 

1  1  22.     Gerhard  tite  

Cu(NO3)2-3Cu(OH)2 

Ortho. 

1123.     Darapskite  

NaNO3-Na2SO4-H2O 

Tetrag. 

1124.    Nitroglauberite  

6NaNO3  -  2Na2SO4  •  3H2O 

Tetrag. 

1125      Lautarite 

Ca(IO3)2 

Mono. 

1126      Dietzeite 

yCa(IO3)2  '8CaCrO4 

Mono. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


261 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

nog. 

Yellowish 

3 

2 

Thuringia 

Phosphorus 

i  no 

Yellowish 

Belgium 

\. 

IIII. 

Brown 

2 

2 

Saxony 

>Arsemc 

III2. 

Yellow 

5 

3 

Sweden 

Phosphorus 

1113. 

Green 

4 

4 

Cork 

Lead 

1114. 

Green 

2  5 

Joachimsthal 

Copper 

2 

Hannover 

Phosphorus 

ri  16. 

Brownish 

Greece 

Arsenic 

1117. 

White 

2 

Nevada 

1118. 

White 

2 

2 

Egypt 

IIIQ. 

Gray 

Kentucky 

Fertilizer 

1  1  20. 

White 

Kentucky 

II2I. 

Colorless 

Chile 

1122. 

Green 

2 

3 

Arizona 

Copper 

1123. 

Colorless 

Chile 

Soda 

1124. 

White 

Atacama 

Sodium 

1125. 
1126. 

Colorless 
Yellow 

3 

4-5 
3-7 

Atacama 
Atacama 

Iodine 

262 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


• 

Composition 

Form 

X.      BORATES,   ETC. 

1127.    Sussexite  

2  (Mn,Zn,Mg)  O  •  B2O3  •  H2O 

Ortho. 

1128.    Ludwigite 

3MgO  •  B2O3  •  FeO  •  Fe2O3 

Ortho 

1129.     Pinakiolite 

3MgO  •  B2O3  •  MnO  •  Mn2O3 

Ortho. 

1130.    Nordenskioldine  
1131.    Jeremejevite 

CaSn(BO3)2 
A1BO3 

Regular 
Hexag. 

1132.    Hambergite   

Be2(OH)BO3 

Ortho. 

1133.     Szaibelyite  

2MgsB4Oii-3H2O 

Ortho. 

1134.     Boracite   

MgvCLBrfOso 

Regular 

1135      Ascharite 

3Mg2B2Os-2H2O 

Amorph. 

1136      Rhodizite 

K  Al  Cs  Rb,Na,Ca,Mg,Al,  borate 

Regular 

1137.    Warwick!  te 

6MgO  •  FeO  •  2TiO2  •  3B2O3 

Ortho. 

1138.    Howlite 

HsCa2B5SiOi4 

Ortho. 

1139.    Lagonite              ...    . 

Fe2O3'3B2O3-3H2O 

Earthy 

1140.    Larderellite  

(NH4)2O--  4B2O3  •  4H2O 

Mono. 

1141.     Colemanite  

CazBeOu  •  5H2O 

Mono. 

1142.     Pinnoite       

MgB2O4-3H2O 

Tetrag. 

1143.    Heintzite  

K2O  •  4MgO  •  9B2O3  •  1  6H2O 

Mono. 

1144.     Borax  

Na2B4O7-ioH2O 

Mono. 

1145.     Ulexite  

NaCaB5O9'8H2O 

Fibers 

1146.     Bechilite  

CaB4O7-4H2O 

Crusts 

1147.    Hydroboracite  
1148.     Sulfoborite 

CaMgB6On-6H20 
3MgSO4  •  2Mg3B4O9  •  1  2H2O 

Mono. 
Ortho. 

1149.     Uraninite 

Pb,Th,G,Ce,La,Y,Ca,N,Fe,H,  uranite 

Regular 

1150.     Uranniobite  .       ... 

Pb,Th,G,Ce,La,Y,Ca,N,Fe,H,  uranite 

Regular 

1  15  it    Broggerite   

Pb,Th,G,Ce,La,Y,Ca,N,Fe,H,  uranite 

Regular 

1152.     Cleveite  

Pb,Th,G,Ce,La,Y,Ca,N,Fe,H,  more  U 

Regular 

1153.     Nivenite  

Pb,Th,G,Ce,La,Y,Ca,N,Fe,H,  more  U 

Regular 

1154.     Pitchblende  

Pb,Th,G,Ce,La,Y,Ca,N,Fe,H,more  U 

Regular 

1155.     Carnotite 

K2O  •  2U2O3  •  V2OS  •  3H2O 

Earthy 

1156.     Gummite 

(Pb,Ca,Ba)U3SiOi2  •  6H2O 

Amorph. 

1157.     Yttrogummite 

(Pb,Ca,Ba)U3SiOI2  •  6H2O+  Y 

Earthy 

1158.    Thorogummite 

(Pb,Ca,Ba)U3SiOi2  •  6H2O+Th 

Earthy 

1159.     Uranosphaerite 

(BiO)2U2O7'3H2O 

Globular 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


263 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

1127. 
1128. 

II2Q. 
1130. 
II3I. 
1132. 
1133. 
II34- 
1135. 

White 
Green 
Black 
Yellow 
Colorless 
White 
White 
White 
White 

3 
6 

11 

7-5 
3 
7 

3 
3-9 

3-8 
4 
3 

2 

3 

2-9 

i  .9 

New  Jersey 
Hungary 
Sweden 
Norway 
Mt.  Soktuj 
Norway 
Hungary 
France 
Germany 

Manganese 
Magnesium 
Manganese 
Zinc 
Boron 
Berylium 

1136. 

II37- 
II38. 
Il^g. 

White 
Brown 
White 
Yellow 

8 
3 
3-5 

3 
3 

2 

Urals 
New  York 
Nova  Scotia 
Tuscany 

II4O. 

Yellow 

Tuscany 

II4I. 
1142. 

1143- 
1144. 

H45- 
1146. 

Colorless 
Yellow 
Colorless 
White 
White 
Gray 

4 
3 

4 

2 

I 

2 

3 

2 

1.6 
1.6 

California 
Stassfurt 
Stassfurt 
Nevada 
Nevada 
Tuscany 

>  Boron 

1147. 
1148. 
1149. 
1150. 
II5I. 
II52. 
1153- 
IIS4- 
1155. 

White 
Colorless 
Gray 
Gray 
Gray 
Gray 
Black 
Black 
Yellow 

2 

4 
5-5 
5-5 
5-5 
5-5 
5-5 
5-5 

1.9 

2 

9 
9 
9 

8 
8 

Caucasus 
Germany 
Connecticut 
Norway 
Norway 
Norway 
Texas 
Colorado 
Utah 

•Rare  elements 

1156. 

II57- 
IIS8. 

II59- 

Yellow 
Black 
Brown 
Red 

2-5 

5 
4 

2-3 

3-9 

4 
6 

North  Carolina 
Norway 
Texas 
Saxony 

264 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

XI.    SULPHATES,  ETC. 
i.  Anhydrous  Sulphates 
1  1  60.     Mascagnite 

(NH4)2SO4 

Ortho 

1161.    Tavlorite 

5K2SO4-(NH4)2SO4 

Concret. 

1162.     Thenardite  
1163.     Aphthitalite  

Na2SO4 

(K,Na)2SO4 

Ortho. 
Hexag. 

1164.     Glauberite  

Na2SO4-CaSO4 

Mono. 

1165.    Langbeinite  

K2Mg2(SO4)3 

Hexag. 

1166.    Barite  

BaSO4 

Ortho. 

1167.     Bologna  stone  

BaSO4 

Ortho. 

1168.     Cawk  

BaSO4 

Ortho. 

1169.     Michel-levyte  

BaSO4 

Ortho. 

1  1  70.     Celestite 

SrSO4 

Ortho. 

1171.     Apotome 

SrSO4 

Ortho. 

1172.    Anglesite 

PbSO4 

Ortho. 

1173.    Anhydrite 

CaSO4 

Ortho. 

1174.    Vulpinite 

CaSO4 

Scaly 

1175.    Tripstone  

CaSO4 

Concret. 

1176.     Zinkosite  
1177.    Hydrocyanite  
1178.     Crocoite  

ZnS04 
CuS04 
PbCrO4 

Ortho. 
Ortho. 
Mono. 

1179.    Leadhillite 

4PbO-SO3-2CO2-H2O 

Mono. 

1180.     Susannite 

4PbO-SO3-2CO2-H2O 

Mono. 

1  1  8  1  .     Sulphohalite 

3Na2SO4-2NaCl 

Regular 

1182.     Caracolite 

Pb(OH)Cl-Na2SO4 

Ortho. 

1183.     Kainite.  .           

MgSO4-KCl-3H2O 

Mono. 

1184.     Connellite  

CuIS(Cl,OH)4SOl6-  i5H2O 

Hexag. 

1185.     Spangolite   

Cu6AlClSOIO-9H2O 

Hexag. 

1186.    Hanksite  

9Na2SO4-2Na2CO3-KCl 

Hexag. 

1187.     Misenite  

HKSO4 

Mono. 

1  188.     Brochantite  

CuSO4-3Cu(OH)2 

Ortho. 

1189.    Lanarkite  

Pb2SOs 

Mono. 

1190.     Dolerophanite  

Cu2SOs 

Mono. 

119^.     Caledonite  
1192:    Linarite 

2(Pb,Cu)0-S03-H2O 
(Pb,Cu)SO4  •  (Pb,Cu)  (OH)2 

Ortho. 
Mono. 

1193.    Antlerite 

3CuSO4-7Cu(OH)2 

Massive 

1194.     Alumian             

A12O3-2SO3 

Hexag. 

2.  Hydrous  Sulphates 
a.  Normal 
1195.    Lecontite  

(Na,NH4,K)2SO4-2H2O 

Ortho. 

1196.     Mirabilite  

Na2SO4-ioH2O 

Mono. 

1197      Kieserite 

MgSO4-H2O 

Mono. 

1198.     Szmikite 

MnSO4-H2O 

Amorph. 

1  1  oo.     Gypsum 

CaSO4-2H2O 

Mono. 

1  200.     Selenite      

CaSO4-2H2O 

Mono. 

1201.     Satin  spar  : 

CaSO4-2H2O 

Mono. 

1  202.    Alabaster  

CaSO4-2H2O 

Mono. 

1203      Ilesite 

(Mn,Zn  Fe)SO4-4H2O 

Mono. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


265 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

1160. 

Yellow 
White 

2 
2 

1-7 

Etna 
Chincha  Islands 

jSulphur 

1162. 
1163. 
1164. 
ii6<s 

White 
White 
Yellow 
Colorless 

2 

3 

2-5 

2 
2 

2-7 
2    8 

California. 
Vesuvius 
California 
Germany 

Sulphur 
Potash 
Potassium 
Manganese 

1166. 
1167. 
1168. 
1169. 
1170. 
1171. 
1172. 

"73- 

1174. 

1175- 
1176. 

White 
Reddish 
Reddish 
Reddish 
White 
White 
White 
White 
White 
White 
White 

2.5 
2.5 
2.5 
2.5 

3 
3 
2-7 
3 
3 
3 

4 
4 
4 
4 
3-9 
3-9 
6 

2.8 
2.8 
2.8 
2.8 

New  York 
Bologna 
Bologna 
Quebec 
Texas 
Texas 
Pennsylvania 
Tennessee 
Lombardy 
Lombardy 
Spain 

Barium 

jStrontium 
Lead 

>  Calcium 
Zinc 

1177. 

Green 

Vesuvius 

Copper 

1178. 
1179. 
1  1  80. 
1181. 
1182. 

Red 
Yellow 
Yellow 
Yellow 
Colorless 

2-5 
2-5 

2-5 

3 
4.5 

5-9 
6 
6  - 

2 

Arizona 
Scotland 
Scotland 
California 
Atacama 

[Lead 

Sulphur 
Lead 

1183. 
1184. 
1185. 
1186. 

1187. 

White 
Blue 
Green 
White 
White 

2 

3 

2 

3 

2 

3 
3 
2-5 

Stassfurt 
Cornwall 
Arizona 
California 
Naples 

Sulphur 
>Copper 

Sodium 
Potassium 

1188. 
1189. 

IIQO. 

Green 
White 
Brown 

3-5. 

2 

3-9 

5 

Colorado 
Scotland 
Vesuvius 

Ee°aTr 
Copper 

1191. 

1192. 
IIQ3. 

Green 
Blue 
Green 

2-5 
2 

6 
5 

3  -0 

California 
California 
Arizona 

JLead 
Copper 

1194. 
HOS. 

White 
Colorless 

2 
2 

2-7 

Spain 
Central  America 

Sulphur 

lc    j- 

1196. 
1197- 
1198. 
1199. 

I2OO. 
I2OI. 
I2O2. 
I2OV 

White 
White 
White 
White 
White 
White 
White 
Green 

i-5 
3 

•  5 
•  5 
•  5 
-5 
•5 

i 

2 

3 

2 
2 
2 
2 

Salt  Lake,  Utah 
Stassfurt 
Hungary 
Michigan 
Michigan 
Michigan 
Michigan 
Colorado 

>  Sodium 

Magnesium 
Manganese 

^Piaster 

Ornaments 
Manganese 

266 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

XI.    SULPHATES,  ETC.  — 
continued 
1  204.     Epsomite  

MgSO4-7H2O 

Ortho 

1  205  .     Goslarite 

ZnSO4-7H2O 

Ortho 

1206.     Morenosite  
1207.     Melanterite  
1208.     Mallardite  
1209.     Pisanite          

NiS04-7H20 
FeS04-7H20 
MnS04-7H20 
(Fe,Cu)SO4-7H2O 

Ortho. 
Mono. 
Mono. 
M!ono 

1210      Salvadorite  

(Cu,Fe)SO4-7H2O 

]VIono 

121  1.     Bieberite  

CoSO4-7H2O 

M!ono 

1212.     Chalcanthite  

CuSO4-5H2O 

Triclinic 

1213.     Syngenite  

CaSO4-K2SO4-H2O 

]Vlono 

1214.    Loweite 

MgSO4  •  Na2SO4  •  2^H2O 

Tetrae 

1215.     Blodite 

MgSO4  •  Na2SO4  •  4H2O 

jyjono 

1216.    Leonite 

MgSO4-K2SO4-4H2O 

M!ono 

1217.     Boussingaultite 

(NH4)2SO4  •  MgSO4  •  6H2O 

]VIono 

1218.     Picromerite 

MgSO4-K2SO4-6H2O 

M!ono 

1219.     Polyhalite  

2CaSO4  •  MgSO4  •  K2SO4  •  2H2O 

jVIono 

1  2  20.     Pickering!  te  

MgSO4-Al2(SO4)3-22H2O 

Mono 

1  22  1.    Halotrichite  

FeSO4  •  A12(SO4)3  •  24H2O 

Mono. 

1222.    Apjohnite  

MnSO4  •  A12(SO4)3  •  24H2O 

Mono. 

1223.    Dietrichite  

(Zn,Fe,Mn)SO4-Al,(SO4V22H«0 

Mono. 

1224.    Masrite  

Fe,Ms,Mn,Co,Al,  sulphate 

Fibrous 

1225.     Coquimbite 

Fe2(SO4)3-9H2O 

Hexag 

1226.    Quenstedtite 

Fe2(SO4)3-ioH2O 

JV^ono 

1227.     Ihleite 

Fe2(SO4)3-i2H2O 

Efflor 

1228.    Alunogen     

Al2(SO4)3-i8H2O 

Mono. 

1229.     Krohnkite     

CuSO4-Na2SO4-2H2O 

Mono. 

1230.     Phillipite   

CuSO4  •  Fe2(SO4)3  •  wH2O 

Mono. 

1231.     Ferronatrite  

3Na2SO4  •  Fe2(SO4)3  •  6H2O 

Hexag. 

1232.     Romerite  

FeSO4-Fe2(SO4)3-i2H2O 

Triclinic 

1233.     Natrochalcite  

Na2SO4-  Cu4(OH)2(SO4)2-  2H2O 

Mono. 

b.  Basic 
1  234     Langite 

CuSO4-3Cu(OH)2-H2O 

Ortho. 

1235.    Herrengrundite  
1236.     Kamarezi  te 

2  (CuOH)2S04  •  Cu(OH>2  •  3H2O 
(CuOH)2SO4  •  Cu(OH)2  •  6H2O 

Mono. 
Ortho. 

1237.     Cyanotrichite.  .  
1  238      Serpierite     

4CuO-AlA'SO3-8H2O 
Cu,Zn,  sulphate 

Ortho. 
Ortho. 

1239.     Copiapite  

2  Fe2O3  •  5  SO3  •  1  8H2O 

Mono. 

1  240.     Castanite  

Fe2O32SO3-8H2O 

Mono. 

1241.     Utahite  

3Fe2O3-2SO3-7H2O 

Hexag. 

1242.    Amarantite  

Fe2O3-2SO3-7H2O 

Triclinic 

1243.     Fibroferrite 

Fe2O3'2SO3-ioH2O 

Mono. 

1  244.     Raimondite 

2Fe2O3'3SO37H2O 

Hexag. 

1245.     Carphosid  erite  

3  Fe2O3  •  4SO3  •  i  oH2O 

Hexag. 

1246.     Glockerite   

2Fe2O3-SO3-6H2O 

Earthy 

1247.     Knoxvillite  

Cr,Fe,Al,H,  sulphate 

Ortho. 

1  248.    Redingtonite 

Cr  Fe  Al  H,  sulphate 

Ortho. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


267 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

1204. 
1205. 
1206. 
1207. 
1208. 

White 
White 
Green 
Green 
Colorless 

2 
2 
2 
2 

1-7 
1.9 

2 

1.8 

Kentucky 
Montana 
Galicia 
Utah 
Utah 

Medicine 
Zinc 
Nickel 
Iron 
Manganese 

1  200. 

Blue 

Turkey 

\- 

I2IO. 

Green 

Chile 

JCopper 

I2II. 

Red 

I    0 

Bieber 

Cobalt 

1212. 
I2I3. 
1214. 
I2IS. 

1216. 

Blue 
Colorless 
Yellow 
Colorless 
White 

2-5 
2 
2 
2 

2 
2 
2 
2 

Arizona 
Galicia 
Austria 
Chile 
Germany 

Copper 
Potassium 
Sodium 
Magnesium 
Potassium 

1217. 

White 

1.6 

Tuscany 

Magnesium 

1218. 

White 

2 

Vesuvius 

Potassium 

1219. 
I22O. 

Red 
White 

2 

I 

2 

Austria 
Colorado 

Calcium 

} 

1221. 

Yellow 

New  Mexico 

Li  • 

1222. 
1223. 

Yellow 
Yellow 

1.5 

2 

1-7 

Tennessee 
Hungary 

>Alummum 

1224. 

EsrvDt 

1225. 
1226. 
1227. 

White 
Red 
Yellow 

2 
2 

2 
2 
I    8 

Chile 
Chilel 
Bohemia 

|lron 

1228. 
I22Q. 
I23O. 

White 
Blue 
Blue 

1-5 

2.5 

1.6 
1.9 

Bohemia 
Atacama 
Chile 

Aluminum 
JCopper 

I23I. 
1232. 
1233- 

1234. 
1235- 
1236. 
1237. 

Gray 
Brown 
Green 

Blue 
Green 
Green 
Blue 

2 

3 
4 

2 
2 
3 

2 
2 
2 

3 

3 
3 

Chile 
Chile 
Chile 

Cornwall 
Hungary 
Greece 
Utah 

Sodium 
Iron 
Copper 

Copper 

1238. 

Green 

Greece 

1239. 
I24O. 
1241. 

Yellow 
Brown 
Yellow 

2-5 

3 

2 
2 

Chile 
Chile 
Utah 

1242. 
1243. 
1244. 

1245- 
1246. 
1247. 
1248. 

Red 
Yellow 
Yellow 
Yellow 
Brown 
Yellow 
Pale  purple 

2 
2 

3 

4 

2 
1.8 

3 

2 

i-7 

Chile 
Chile 
Bolivia 
Greenland 
Harz 
California 
Knoxville 

Iron 
Chromium 

268 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

XL    SULPHATES,  ETC.  — 
continued 
1249.     Cyprusite  

7Fe2O3  •  A12O3  •  ioSO3  •  i4H2O 

Hexag 

1250.     Aluminite  

A12O3-SO8-9H2O 

Mono 

1251.    Paraluminite  

2Al2O3-SO3-i5H2O 

Mono. 

1252.     Felsobanyite  

2Al2O3-SO3-ioH2O 

Ortho. 

1253.     Botryogen 

MgO  •  FeO  •  Fe2O34SO3  •  1  8H2O 

Mono 

1254.     Siderona  tri  te 

2Na2O  •  Fe2O34SO3  •  yH2O 

Ortho 

1255.    Voltaite 

5  (K2,Fe)O  -  2  (Al,Fe)2O3  •  ioSO3  •  i  sH2O 

Regular 

1256.     Metavoltine  

5  (Ka2Na2,Fe)O  •  3F2O3  •  1  2SO3  •  i8H2O 

Hexag. 

1257.    Alunite  

K2O  •  3  A12O3  •  4SO3  •  6H2O 

Hexag. 

1258.    Jarosite  

K2O  •  3  Fe2O3  •  4SO3  •  6H2O 

Hexag. 

1259.    Lowigite  

K2O-3A12O3-4SO3-9H2O 

Hexag. 

1260.     Ettringite  

6CaO  •  A12O3  •  3SO3  •  33H2O 

Hexag. 

1261.    Quetenite  

MgO  •  Fe2O3  •  3SO3  •  i3H2O 

Mono. 

1262.    Zincaluminite 

2ZnSO4  •  4Zn(OH)2  •  6  A1(OH)3  •  5H2O 

Hexag. 

1263.    Johannite 

U,Cu,H,  sulphate 

Mono. 

1  264.     Uranopilite  
3.  Tellurates 
1265.     Montanite   

CaU8S203I-25H20 
Bi2O3-TeO3-2H2O 

Incrust. 
Earthy 

1266.     Emmonsite  

Fe,H,  tellurate 

Mono. 

1267.     Durdenite  

Fe2(TeO3)3-4H2O 

Massive 

1268.     Chalcomenite  

CuSeO3  •  2H2O 

Mono. 

1269.     Molybdomenite  

Pb,  selenite 

Ortho. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


269 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

1249. 

Yellow 

2 

Cyprus 

Iron 

1250. 

White 

I 

I 

Halle 

1 

1251. 

White 

Halle 

}  Aluminum 

1252. 

Snow  white 

I 

2 

Hungary 

J253- 

Red 

2 

2 

Sweden 

| 

1254. 

Yellow 

2 

2 

Chile 

1255- 

Green 

3 

2 

Naples 

/.iron 

1256. 

Yellow 

2 

2 

Persia 

j 

1257. 

White 

3-5 

2-5 

Colorado 

Aluminum 

1258. 

Yellow 

2-5 

3 

Utah 

Iron 

1259. 

Yellow 

3 

2 

Upper  Silesia 

Aluminum 

1260. 

Colorless 

2 

1-7 

Prussia 

Calcium 

1261. 

Brown 

3 

2 

Chile 

Iron 

1262. 

White 

2 

2 

Greece 

Zinc 

1263. 

1264. 

Green 
Yellow 

2 

3 

Joachimsthal 
Tohanngeorgenst'dt 

>Uranium 

1265. 

Yellow 

Montana 

} 

Bismuth 

1266. 

1267. 

Green 
Yellow 

5 
2 

Arizona 
Honduras 

JTellurium 

1268. 

1269. 

Blue 
White 



3 

Argentina 
Argentina 

}  Selenium 

270 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

XII.      TUNGSTATES,    MOLYB- 
DATES 

1270.    Wolframite  

(Fe,Mn)WO4 

Mono. 

1271.    Hiibnerite  

MnWO4 

Mono. 

1272      Scheelite 

CaWO4 

Tetrag 

1273.     Cuprotungstite  
1274.     Po  wellite 

CuWO4 
CaMoWO4 

Crystal. 
Tetrag. 

1275.     Stolzite  .             

PbWO4 

Tetrag. 

1276.    Raspite    

PbWO4 

Mono. 

1277.     Wulfenite  

PbMoO4 

Tetrag. 

1278.     Reinite  

FeWO4 

Tetrag. 

1279.     Belonesite  

MgMoO4 

Tetrag. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


271 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

1270. 

Black 

5 

7 

Connecticut 

| 

1271. 
1272. 

Brown 
White 

5-5 
4-5 

7 
5-9 

Nevada 
North  Carolina 

>Tungsten 

1273. 

Green 

4 

Chile 

j 

1274. 

Yellow 

3-5 

4 

Michigan 

Molybdenum 

1275- 
1276. 

Green 
Yellow 

2.7 

2 

7.8 

Zinnwald 
New  South  Wales 

>Tungsten 

1277. 

Green 

2.7 

6.7 

Arizona 

Molybdenum 

1278. 
1270. 

Brown 
White 

4 

6.6 

Japan 

Vesuvius 

Tungsten 
Molybdenum 

272 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

XIII.    ORGANIC  ACIDS 

Oxalates,  Mellates 
1280.    Whewellite  

CaC2O4-H2O 

Mono. 

1281.     Oxammite  

(NH4)2C2O4-2H2O 

Ortho. 

1282      Humboldtine 

2FeC2O4-3H2O 

Capill. 

1283     Mellite 

Al2Ci2Oi2-i8H2O 

Tetrag. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


273 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

1280. 

Colorless 

2    ^ 

Saxony 

Calcium 

1281. 

Yellowish 

Peru 

Ammoni  u  m 

1282. 
1283. 

Yellow 
Yellow 

2 
2 

2 

i-S 

Bohemia 
Bohemia 

Iron 
Mellitic  acid 

274 


GUIDE  TO  MINERAL  COLLECTIONS 

COMPREHENSIVE 


Composition 

Form 

XIV.    HYDROCARBONS 
1284.     Scheererite 

IVIono 

1285.     Hatchettite        .    . 

£_g-o/.   jj_I-m' 

Mono 

1286.     Paraffin 

C  =  85%;  H=is% 

Amorph 

1287.     Ozocerite         .... 

C  =  86%;  H=i4% 

Amorph 

1288.     Zietrisikite  
1289.     Chrismatite  

CnRm. 

C  =  84.6%;  H=iS.4% 
C  =  8o%;  H  =  2o% 

Amorph. 
Amorph. 

1290.     Urpethite  
1291.     Fichtelite  
1292.     Napalite  

CiSH2s. 
C3H4. 

C  =  85.8%;  H=i4.2% 
C  =  87.2%;  H=i2.8% 
C  =  89.8%;  H=io.2% 

Amorph. 
Mono. 
Amorph. 

1293.     Amber  

0  =  78.9%;   H=io.5%; 

Amorph. 

1  294.     Succinite 

CnHm 

O=io.6% 
0  =  78  9%;   H=io  *%; 

Amorph. 

1295.     Retinite                 .    . 

0=io.6% 

Amorph. 

1296.     Gedanite            .    . 

Amorph. 

1297.     Glessite  
1298.     Rumanite  

Amorph. 
Amorph. 

1299.     Copalite  

0  =  85.6%;  H=n.4%; 

Amorph. 

1300.     Bathvillite  

CnRm. 

0  =  3% 

Amorph. 

1301.     Tasmanite  
1302.     Dysodile  

CnRm. 
CnRm. 

Ash  =  3i% 
C  =  79%;  H  =  io%;  O  =  s%; 

C  =  69%;H=io%;O=i6%; 

Scales 
Scales 

1303.     Geocerite  

C28H,,6O2. 

S  =  3%;  N=2% 
C  =  79%;  H=i3%;  O  =  8% 

Waxy 

1304.     Leucopetrite  

C  =  82%;  H=n%;  O  =  7% 

Waxy 

1305.     Pyroretinite  

C40H60O 

C  =  8o%;  H  =  9%;  O=n% 

Resinous 

1306.     Dopplerite 

C  H 

Cr-TC7  •    TT       i-C7  •    C\       A  O7  . 

Amorph. 

1307.     Idrialite 

C42HI4O. 

N=i% 
C  =  9i%;  H  =  6%;  0  =  3% 

Earthy 

1308.     Posepnyte  

1309.     Petroleum,  naphtha.  . 
1310.     Pittasphalt  

C22H3604. 

CwHaw+2 

C  =  72%;  H=io%; 
O=i8% 

Plates 

Amorph. 
Viscid 

1311      Asphaltum 

Amorph. 

1312      Elaterite 

Amorph. 

1313.     Albertite 

Amorph. 

1314.     Grahamite 

C  H2 

Amorph. 

1315.     Gilsonite  
1316.     Mineral  coal 
1317      Anthracite 

CnH2»-f-2 

Amorph. 
Amorph. 
Amorph. 

1318      Bituminous  coal 

Amorph. 

1319      Coking  coal 

C«H2» 

Amorph. 

1320.     Non-coking  coal  
1321.     Cannel  coal.  
1322.     Torbanite  
1323.     Lignite  

C»H2W 

Amorph. 
Amorph. 
Amorph. 
Amorph. 

1324.      let 

Amorph. 

1325.     Peat                       .... 

C«H2» 

Amorph. 

COMPREHENSIVE  LIST  OF  MINERALS 
LIST  OF  MINERALS 


275 


No. 

Color 

Hard- 
ness 

Gravity 

Locality 

Chief  Constituent 
or  Use 

1284. 

Resinous 

I 

Switzerland 

Chemicals 

1285. 
1286. 

White 
Yellowish 

I 

•9 

Switzerland 
England 

[Paraffin 

1287. 

Brown 

Q 

Sicily 

• 

1288. 

Brown 

_  r 

•  y 
•9 

Utah 

1280. 

Yellow 

Q 

Saxony 

y 
1290. 

Brown 

V 

.8 

Urpeltz 

1291. 

White 

Bavaria 

1292. 

Brown 

2 

California 

Technical 

1293. 

Yellow 

2 

i 

Baltic  coast 

purposes 

1294. 

Yellow 

2 

i 

Baltic  coast 

J 

!295- 

Brown 

Germany 

1296. 

Brown 

Baltic 

Technical 

1297. 

Brown 

2 

i 

Baltic 

purposes 

1298. 

Brown 

2 

i 

Roumania 

1299. 

Yellow 

i 

Tropics 

Varnish 

1300. 

Brown 

2 

i 

Scotland 

1301. 

Brown 

2 

i 

Tasmania 

Technical 

1302. 

Yellow 

I  .  2 

Sicily 

purposes 

1303. 

White 

\Veissengels 

1304. 

White 

I  .  2 

\Veissengels 

I3«>S- 

Yellow 

2 

I 

Bohemia 

1306. 

Black 

2 

I 

Styria 

Technical 

1307. 

White 

Idria 

purposes 

1308. 

Green 

•9 

California 

1309. 

Brown 

.6 

United  States 

-  —      —  - 

1310. 

Greenish  brown 

Pennsylvania 

}0il 

1311. 

Black 

i 

California 

1312. 

Brown 

9 

Derbyshire 

ISIS- 

Black 

I 

Nova  Scotia 

Technical 

1314- 
1315- 

Black 
Black 

2 

2 

West  Virginia 

Utah 

purposes 

1316. 

Black 

2-5 

United  States 

1317- 
1318. 

Black 
Black 

2 
2-5 

Pennsylvania 
Pennsylvania 

I3I9- 
1320. 

Black 
Black 

2 
2 

•5 
.5 

Virginia 
Illinois 

>Fuel 

1321. 
1322. 

Black 
Brown 

2 
2.2 

•5 
.  i 

West  Virginia 
Scotland 

1323- 

Brown 

1-5 

.  i 

Western  states 

1324. 
1325- 

Black 
Brown 

i-5 

i 

.1 
.  i 

Wales 
Scotland 

Jewelry 
Fuel 

GENERAL  INDEX 


GENERAL  INDEX 


The  number  preceding  each  mineral 
following  is  the  page  number. 


590. 
774- 
81. 
748- 
545' 
565- 
979' 
969. 

493' 


436. 
291. 

664. 
70. 

183- 
90. 

I2O2. 
529. 


5°5- 

374- 
.55- 
61. 

998. 

725- 
10. 

655- 

139- 

3i- 

883. 

646. 

62. 

1194. 

1250. 

1257. 

1228. 

809. 

21. 
1242. 


Abbreviations,  xxi 
Abriachanite,  234 
Acadialite,  242 
Acanthite,  204 
Achroite,  240 
Acmite,  232 
Actinoliie,  232 
Adamite,  254 
Adelite,  252 
Admire,  44 
Adularia,  134,  230 
Aenigmatite,  234 
Aerolites,  43 
Aeschynite,  250 
Agaric  Mineral,  226 
Agate,  90,  218 
Agricola,  198 
Agricolite,  236 
Aguilarite,  204 
Ahnighito,  43 
Aikinite,  210 
Airy's  spiral,  88 
Alabandite,  206 
Alabaster,  264 
Alalite,  230 
Albertite,  274 
Albite,  140,  230 
Alexandrite,  222 
Algodonite,  204 
Alisonite,  204 
Allacite,  254 
Allanite,  240 
Allemonite,  202 
Allochroite,  236 
Alloclasite,  208 
Allopalladium,  202 
Allophane,  246 
Almandite,  159,  236 
Altaite,  204 
Alumian,  264 
Aluminite,  268 
Aluminium,  45 
Alunite,  268 
Alunogen,  266 
Alurgite,  244 
Amalgam,  202 
Amarantite,  266 


the  list  number  used  in  the  List  of  Minerals;  that 


502.  Amazonstone,  230 
1293.  Amber,  187,  274 
975.  Arnblygonite,  252 

830.  Amesite,  244 
277.  Amethyst,  88,  218 
567.  Amianthus,  232 

1108.  Ammiolite,  258 

Amorphous,  2 
563.  Amphibole,  152,  232 
782.  Analcime,  242 
781.  Analcite,  167,  242 
704.  Andalusite,  238 
511.  Andesine,  139,  230 
152.  Andorite,  210 
648.  Andradite,  159,  236 

1084.  Andrewsite,  258 

1172.  Anglesite,  181,  264 

1173.  Anhydrite,  264 
53.  Animikite,  204 

1024.  Annabergite,  256 
929.  Annerodite,  250 
803.  Anomite,  242 
514.  Anorthite,  139,  142,  230 
N   504.  Anorthoclase,  138,  230 
561.  Anthophyllite,  232 
1317.  Anthracite,  192,  274 
850.  Antigorite,  244 

Antimonates,  175 
12.  Antimony,  31,  45,  202 
1193.  Antlerite,  264 
945.  Apatite,  175,  252 
422.  Aphrite,  226 
747.  Aphrizite,  240 

831.  Aphrosiderite,  244 
1163.  Aphthitalite,  264 
1222.  Apjohnite,  266 

658.  Aplome,  236 

758.  Apophyllite,  240 
1171.  Apotome,  264 

596.  Aquamarine,  156,  234 

450.  Aragonite,  122,  226 

735.  Ardennite,  240 
5900.  Arfedsonite,  234 

421.  Argentine,  226 
66.  Argentite,  51,  204 
Argon,  45 

216.  Argyrodite,  212 


279 


280 


GUIDE  TO  MINERAL  COLLECTIONS 


Aristotle,  198 
22.  Arquerite,  202 
Arsenates,  175 
9.  Arsenic,  31,  45,  202 
1003.  Arseniopleite,  254 
997.  Arseniosiderite,  254 
325.  Arsenolite,  220 
134.  Arsenopyrite,  67,  208 
567.  Asbestus,  155,  232 
413.  Asbolite,  224 
1135.  Ascharite,  262 
305.  Asmanite,  218 
616.  Aspasiolite,  234 
1311.  Asphaltum,  188,  274 
910.  Astrophyllite,248 
248.  Atacamite,  214 
1005.  Atelestite,  254 
1098.  Atopite,  258 
1069.  Attacolite,  258 
699.  Auerlite,  238 
1066.  Augelite,  256 
542.  Augite,  147,  232 
467.  Aurichalcite,  228 
365.  Automolite,  222 
1090.  Autunite,  258 
285.  Aventurine,  218 

Avicenna,  198 
33.  Awaruite,  202 

Axial  plane,  131 
727.  Axinite,  240 
465.  Azurite,  130,  228 

Babbitt  metal,  32 
559.  Babingtonite,  232 
389.  Baddeleyite,  222 
726.  Bagrationite,  240 
536.  Baikalite,  232 

Bayly,  W.  S.,  ix,  200 
1166.  Barite,  170,  264 

Barium,  45 
592.  Barkevikite,  234 
1032.  "Barrandite,  256 

Bartholinus,  112,  198 
621.  Barylite,  234 
618.  Barysilite,  234 
457.  Barytocalcite,  226 
297.  Basanite,  218 

Base,  28 

Basic  Phosphates,  256 
524.  Bastite,  230 
847.  Bastite,  244 
460.  Bastnasite,  226 
1300.  Bathvillite,  274 
401.  Bauxite,  222 

Baveno  Twin,  134 
1049.  Bayldonite,  256 

Bayley,  W.  S.,  ix,  200 


1146 
203 

1279 
896 

1073 
584 
785 
877 

1067, 

159 
739 

594. 

944. 
?* 

937. 

1113, 
100. 

I2II, 
1099, 

166, 
801, 


262. 

329. 
13- 
44- 

484. 

129. 

458. 

1318. 
381. 

1215. 

1021. 

412. 

397- 
876. 

2490. 

1167. 
610. 


1144, 

1078. 

no, 


Bechilite,  262 

Beegerite,  212 

Belonesite,  270 

Bementite,  246 

Beraunite,  258 

Bergamaskite,  234 

Bergmannite,  242 

Bergseife,  246 

Berlinite,  258 

Berthierite,  210 

Bertrandite,  240 

Beryl^^,  234 

Beryllium,  45 

Beryllonite,  252 

Berzelianite,  204 

Berzeliite,  252 

Berzelius,  199 

Beudantite,  260 

Beyrichite,  206 

Biaxial,  89 

Bieberite,  266 

Bindheimite,  258 

Binnite,  210 

Biot,  170 

Biotite,  170,  242 

Bipyramid,  25 

Birefringence,  55 

Bischofite,  214 

Bisectrix,  130 

Bismite,  220 

Bismuth,  31,  45,  202 

Bismuthinite,  204* 

Bismutite,  228 

Bismuto-smaltite,  208 

Bismutospharite,  226 

Bisphenoid,  29 

Bituminous  coal,  274 

Bixbyite,  222 

Black  Jack,  53 

Blodite,  266 

Board  of  Museum  Advisers,  iii 

Bobierrite,  254 

Bog  Manganese,  224 

Bog  Ore,  222 

Bole,  246 

Boleite,  214 

Bologna  Stone,  264 

Bonsdorffite,  234 

Boracite,  177,  262 

Borates,  177 

Borax,  177,  262 

Borickite,  258 

Bornite,  56,  206 

Boron,  45 

Bort,  20,  202 

Boston  Society,  95 

Botryoidal,  89,  99 


GENERAL  INDEX 


281 


1253'  Botryogen,  268 
180.  Boulangerite,  210 

Bourg  de  Oisans  Twin,  85 
182.  Bournonite,  210 
1217.  Boussingaultite,  266 
849.  Bowenite,  244 

Boyle,  198 

Brachydome,  26 

Brachypinacoid,  27 
984.  Brackebuschite,  254 
1013.  Brandite,  254 
380.  Braunite,  222 

Bravais,  199 
657.  Bredbergite,  236 
576.  Breislakite,  232 
103.  Breithauptite,  206 

Breithaupt,  199 
441.  Breunnerite,  226 

Brews  ter,  199 
762.  Brewsterite,  242 
1188.  Brochantite,  264 
1151.  Broggerite,  262 

Bromine,  45 
454.  Bromlite,  226 
230.  Bromyrite,  214 
173.  Brongniardite,  210 
522.  Bronzite,  230 
391.  Brookite,  222 

Brown,  A.  P.,  200 
403.  Brucite,  222 

Brush,  200 
1040.  Brushite,  256 

Buck  and  Company,  ix 
720.  Bucklandite,  240 
301.  Buhrstone,  218 

Bunsen,  199 
341.  Bunsenite,  220 
557.  Bustamite,  232 

Butler,  G.  M.,  200 
512.  Bytownite,  139 

1025.  Cabrerite,  256 

315.  Cacholong,  218 
1072.  Cacoxenite,  258 
Cadmium,  45 
Caesium,  45 

280.  Cairngorm,  88,  218 
1320.  Caking  coal,  274 

740.  Calamine,  240 

143.  Calaverite,  208 
1077.  Calcioferrite,  258 

983.  Calciovolborthite,  254 

415.  Calcite,  112,  226 
Calcium,  45 

434.  Calc-sinter,  226 

434.  Calc-Tufa,  116 
1191.  Caledonite,  264 


1034.  Callanite,  256  * 
221.  Calomel,  214 
959.  Campylite,  252 
532.  Canaanite,  232 

Canada  balsam,  129 
628.  Cancrinite,  236 
217.  Canfieldite,  212 
1321.  Cannel  coal,  274 

Canon  Diablo,  44 
602.  Cappelenite,  234 
1182.  Caracolite,  264 

Carbon,  45 

3.  Carbonado,  20,  202 
Carbonates,  112 
Carlsbad  Twin,  134 
939.  Carminite,  252 
260.  Carnallite,  214 
287.  Carnelian,  90,  218 
1155.  Carnotite,  262 
742.  Carpholite,  240 
1245.  Carphosiderite,  266 

114.  Carrollite,  206 
604.  Caryocerite,  234 
897.  Caryopilite,  246 
382.  Cassiterite,  107,  222 

1240.  Castanite,  266 

806.  Caswellite,  242 

601.  Catapleiite,  234 

284.  Cat's-eye,  218 

375.  Cat's  Eye,  222 
1 1 68.  Cawk,  264 

866.  Celadonite,  246 
1170.  Celestite,  180,  264 

517.  Celsian,  230 

886.  Cenosite,  246 

228.  Cerargyrite,  214 

744.  Cerite,  240 
Cerium,  45 

456.  Cerussite,  127,  226 

333.  Cervantite,  220 

360.  Ceylonite-Pleonaste,  220 

773.  Chabazite,  242 
121 2.  Chalcanthite,  266 

286.  Chalcedony,  89,  218 

77.  Chalcocite,  52,  57,  204 
1268.  Chalcomenite,  268 

409.  Chalcophanite,  224 
1055.  Chalcophyllite,  256 

115.  Chalcopyrite,  57,  206 
1083.  Chalcosiderite,  258 

157.  Chalcostibite,  210 
336.  Chalcotrichite,  220 
429.  Chalk,  226 
840.  Chamosite,  244 
1 08 1.  Chenevixite,  258 
296.  Chert,  90 
466.  Chessylite,  228 


282 


GUIDE  TO  MINERAL  COLLECTIONS 


Chester,  124 

503.  Chesterlite,  230 

705.  Chiastolite,  238 

1074.  Childrenite,  258 

57.  Chilenite,  204 

246.  Chiolite,  214 

148.  Chiviatite,  210 

521.  Chladnite,  230 

239.  Chloralluminite,  214 

Chlorine,  45 

814.  Chloritoid,  244 

237.  Chloromagnesite,  214 

549.  Chloromelanite,  232 

890.  Chloropal,  246 

836.  Chlorophaeite,  244 

615.  Chlorophyll! te,  234 

361,  Chlorospinel,  222 

991.  Chondrarsenite,  254 

731.  Chondrodite,  240 

1289.  Chrismatite,  274 

372.  Chromite,  104,  107,  222 
Chromium,  45 

373.  Chrysoberyl,  222 
889.  Chrysocolla,  246 
665.  Chrysolite,  236 
288.  Chrysoprase,  90,  218 
852.  Chrysotile,  244 

1028.  Churchite,  256 

879.  Cimolite,  246 

94.  Cinnabar,  55,  206 

640.  Cinnamon-Stone,  236 

996.  Cirrolite,  254 

279.  Citrine,  88,  218 

209.  Clarite,  212 

326.  Claudetite,  220 

63.  Clausthalite,  204 

354.  Clay  Iron-stone,  220 

398.  Clay-ironstone,  222 

Cleavage,  16 

508.  Cleavelandite,  230 

1152.  Cleveite,  262 

4.  Cliftonite,  202 

821.  Clinochlore,  244 

987,  Clinoclasite,  254 
Clinodomes,  129 

741.  Clinohedrite,  240 

733.  Clinohumite,  240 

Clinopinacoid,  129 

722.  Clinozoisite,  240 

Cloisonne  work,  33 

1316.  Coal,  190 
Cobalt,  45 

119.  Cobaltite,  206 

537.  Coccolite,  232 

130.  Cockscomb  pyrite,  65 

1065.  Coeruleolactite,  256 

39.  Cohenite,  202 


1319.  Coking  Coal,  274 
1141.  Colemanite,  177,  262 

Colloidal  Silica,  90 
1007.  Collophanite,  254 
884.  Collyrite,  246 
651.  Colophonite,  236 
89.  Colorado! te,  206 
925.  Columbite-Tantalite,  250 

Columbium,  45 
352.  Columnar  hematite,  220 
Comprehensive  list,  201 
1048.  Conichalcite,  256 
863.  Connarite,  246 
1184.  Connellite,  264 
1299.  Copalite,  274 
1239.  Copiapite,  266 

18.  Copper,  38,  45,  202 
1225.  Coquimbite,  266 
1052.  Cornwallite,  256 
829.  Corundophilite,  244 
346.  Corundum,  94,  220 
121.  Corynite,  206 
171.  Cosalite,  210 
243.  Cotunnite,  214 
687.  Couseranite,  238 
95.  Covellite,  206 

Crayon,  173 
378.  Crednerite,  222 
306.  Cristobalite,  218 
589.  Crocidolite,  234 
1178.  Crocoite,  264 

Cronstedt,  198 
838.  Cronstedite,  244 
75.  Crookesite,  204 
591.  Crossite,  234 
245.  Cryolite,  80,  214 

Crystal  form,  2 
113.  Cubanite,  206 
Cube,  33 

Cullinan  diamond,  22 
2496.  Cumengite,  214 
572.  Cummingtonite,  232 
335.  Cuprite,  92,  220 
149.  Cuprobismutite,  210 
233.  Cuproiodargyrite,  214 
60.  Cuproplumbite,  204 
1273.  Cuprotungstite,  270 
730.  Cuspidine,  240 
707.  Cyanite,  163,  238 
1237.  Cyanotrichite,  266 
516.  Cyclopite,  230 
219.  Cylindrite,  212 
694.  Cyprine,  238 
1249.  Cyprusite,  268 


GENERAL  INDEX 


283 


792.  Damourite,  242 

Dana,  ix,  199 
135.  Danaite,  208 
635.  Danalite,  236 
700.  Danburite,  238 
573.  Dannemorite,  232 
1123.  Darapskite,  260 
708.  Datolite,  238 

Daubree,  109,  199 
259.  Daubreeite,  214 
112.  Daubreelite,  206 
597.  Davidsonite,  234 
255.  Daviesite,  214 
470.  Dawsonite,  228 
982.  Dechenite,  254 

833.    061658^244 

650.  Demantoid,  236 
1105..  Derbylite,  258 

Des  Cloizeaux,  199 
980.  Descloizite,  254 
1 1 10.  Destinezite,  260 
855.  Deweylite,  246 
832.  Diabantite,  244 
1109.  Diadochite,  260 
538.  Diallage,  232 

i.  Diamond,  5,  202 
177.  Diaphorite,  210 
393.  Diaspore,  222 

Dichroscope,  96 
1010.  Dickinsonite,  254 
1223.  Dietrichite,  266 
1126.  Dietzeite,  260 
989.  Dihydrite,  254 

Dimorphism,  123 
527.  Diopside,  147,  230 
678.  Dioptase,  238 
Dioscorides,  61 
Dioxides,  107 
Diploid,  62 
686.  Dipyre,  238 
Dispersion,  19 
Disulphides,  206 
Ditetragonal  Bipyramid,  58 
Ditetragonal  Prism,  58 
Ditrigonal  polar,  166 
Doctor  of  Medicine,  3 
>     Dodecahedron,  72 
416.  Dog-tooth  Spar,  226 
1190.  Dolerophanite,  264 
439.  Dolomite,  117,  226 

Dome,  26 

54.  Domeykite,  204 
1306.  Dopplerite,  274 

Double  refraction,  55 
261.  Douglasite,  214 

Drills,  20 
993.  Dufrenite,  254 


169.  Dufrenoysite,  210 
749.  Dumortierite,  240 
974.  Durangite,  252 
1267.  Durdenite,  268 
917.  Dysanalyte,  248 
50.  Dyscrasite,  204 
366.  Dysluite,  222 
1302.  Dysodile,  274 
Dysprosium,  45 


953- 

IIO2. 

578. 
783- 
624. 

1312. 
16. 


600. 
229. 
181. 
595- 
349- 
1266. 
156. 
208. 
960. 
520. 

1075- 
213. 

834- 
491. 
717. 
214. 

763. 
1204. 


1023. 

264. 
98. 

613- 
1260. 

73- 
1047. 

599- 
710. 
626. 
598. 
636. 
95i. 
835. 


Earthy  Apatite;  Osteolite,  252 

Ecdemite,  258 

Edenite,  232 

Edingtonite,  242 

Elaeolite,  234 

Elasticity  coefficient,  119 

Elaterite,  274 

Electrum,  202 

Elements,  4 

Elements,  List  of,  5,  45 

Elpidite,  234 

Embolite,  214 

Embrithite,  210 

Emerald,  156,  234 

Emery,  94,  220 

Emmonsite,  268 

Emplectite,  210 

Enargite,  212 

Endlichite,  252 

Enstatite,  146,  230 

Entantiomorphous,  86 

Eosphorite,  258 

Epiboulangerite,  212 

Epichlorite,  244 

Epididymite,  230 

Epidote,  238 

Epigenite,  212 

Epistilbite,  242 

Epspmite,  266 

Erbium,  45 

Erinite,  254 

Erni,  200 

Erubiscite,  56 

Erythrite,  254 

Erythrosiderite,  216 

Erythrozincite,  206 

Esmarkite,  234 

Ettringite,  268 

Eucairite,  204 

Euchroite,  256 

Eucolite,  234 

Euclase,  238 

Eucryptite,  236 

Eudialyte,  234 

Eulytite,  236 

Eupyrchroite,  252 

Euralite,  244 


284 


GUIDE.  TO  MINERAL  COLLECTIONS 


Europium,  45 
981.  Eusynchite,  254 
933.  Euxenite,  250 
1064.  Evansite,  256 

Extraordinary  ray,  55 


611 

1014 

192 

211 

544 

672 

1252 

923 

1231 
1243 
1291 

253 
ion 

310, 
1058, 

1000, 

295' 
322. 

45i- 
266. 


257 
419' 

273- 
1044- 

670. 
558- 

2l8. 

948. 

369- 

.  196. 

176. 

860. 

679. 

80. 

796. 

869. 


Fahlerz,  74 

Fahlunite,  234 

Fairfieldite,  254 

Falkenhaynite,  212 

Famantinite,  212 

Farrington,  O.  C.,  ix,  200 

Fassaite,  232 

Fayalite,  238 

Felsobanyite,  268 

Fergusonite,  250 

Ferrites,  104 

Ferronatrite,  266 

Fibroferrite,  266 

Fichtelite,  274 

Fiedlerite,  214 

Fillowite,  254 

Finds,  43 

Fire  Opal,  218 

Fischerite,  256 

Flinkite,  254 

Flint,  218 

Float  stone,  220 

Flosferri,  226 

Fluellite,  216 

Fluorescence,  79 

Fluorine,  45 

Fluocerite,  214 

Fluorite,  78,  214 

Fontainebleau  Limestone,  226 

Foote,  W.  M.,  ix 

Footeite,  216 

Forbesite,  256 

Ford,  199,  200 

Forest,3 

Forsterite,  236 

Fossil  resins,  187 

Fouque,  199 

Fowlerite,  232 

Fracture,  16 

Franckeite,  212 

Francolite,  252 

Franklinite,  106,  222 

Freibergite,  212 

Freieslebenite,  210 

French  chalk,  246 

Friedelite,  238 

Frieseite,  204 

Fuchsite,  242 

Fuller's  Earth,  174 

Fulton,  200 


711.  Gadolinite,  238 
Gadolinium,  45 
364.  Gahnite,  222 
59.  Galena,  48,  204 
158.  Galenobismutite,  210 

Gallium,  45 
619.  Ganomalite,  234 
755.  Ganophyllite,  240 
638.  Garnet,  158,  236 
857.  Garnierite,  246 
588.  Gastaldite,  234 
475.  GayLussite,  228 
270.  Gearksutite,  216 
1296.  Gedanite,  274 
562.  Gedrite,  232 
692.  Gehlenite,  238 
Geikielite,  248 
918.  Geikielite,  248 

General  Guide,  v 
856.  Genthite,  246 
1303.  Geocerite,  274 
202.  Geocronite,  212 
1 122.  Gerhardtite,  260 

Germanium,  45 
120.  Gersdorffite,  206 
133.  Geyerite,  208 
321.  Geyserite,  92,  218 

Ghost  quartz,  87 
405.  Gibbsite,  222 
625.  Gieseckite,  236 
794.  Gilbertite,  242 
1315.  Gilsonite,  274     • 
311.  Girasol,  218 
768.  Gismondite,  242 
1164.  Glauberite,  264 
138.  Glaucodot,  208 
684.  Glaucolite,  238 
867.  Glauconite,  246 
587.  Glaucophane,  234 
326.  Glaudetite,  220 
1297.  Glessite,  274 

Glide  planes,  47 
1246.  Glockerite,  266 

Glucinum,  45 
778.  Gmelinite,  242 

Goethe,  102 
394.  Goethite,  101,  222 

15.  Gold,  32,  45,  202 
1205.  Goslarite,  266 
1086.  Goyazite,  258 
1314.  Grahamite,  274 
893.  Graminite,  246 
5.  Graphite,  23,  202 

Gratacap,  200 
96.  Greenockite,  206 
905.  Greenovite,  248 
639.  Grossularite,  159,  236 


GENERAL  INDEX 


285 


Groth,  ix,  200 
906.  Grothite,  248 
107.  Grunauite,  206 
574.  Grunerite,  232 
86.  Guadalcazarite,  206 
45.  Guanajuatite,  204 
908.  Guarinite,  248 
187.  Guitermanite,  210 
1156.  Gummite,  262 
1199.  Gypsum,  182,  264 
757.  Gyrolite,  240 

Haidinger,  65 
1038.  Haidingerite,  256 
224.  Halite,  76,  214 
872.  Halloysite,  246 

Haloids,  76 

1 22 1.  Halotrichite,  266 

1132.  Hambergite,  262 

973.  Hamlinite,  252 

Hancock  County,  87  ' 
1 1 86.  Hanksite,  264 
972.  Harderite,  252 

Hardin  County,  79 
Hardness,  Scale  of,  17 
766.  Harmotome,  242 
729.  Harstigite,  240 
586.  Hastingsite,  234 
1285.  Hatchettite,  274 
920.  Hatchettolite,  250 
1 01.  Hauchecornite,  206 
117.  Hauerite,  206 

Haiiy,  198 
631.  Haiiynite,  236 
804.  Haughtonite,  242 
376.  Hausmannite,  222 
775.  Haydenite,  242 

Heat  conductivity,  30 
534.  Hedenbergite,  232 
962.  Hedyphane,  252 
1143.'  Heintzite,  262 
-290.  Heliotrope,  90 

Helium,  45 
634.  Helvite,  236 
1046.  Hemafibrite,  256 
350.  Hematite,  97,  220 
1001.  Hematolite,  254 
Hemihedral,  70 
Hemimorphic,  93 
Hennepin,  191 
1082.  Henwoodite,  258 
130.  Hepatic  Pyrite,  64 
363.  Heroynite,  222 
1235.  Herrengrundite,  266 
777.  Herschelite,  242 
68.  Hessite,  204 


Hexagonal  system,  68 

Hexatetrahedron,  15 

Hexoctahedron,  12 
761.  Heulandite,  242 
547.  Hiddenite,  232 
930.  Hielmite,  250 
247.  Hieratite,  214 
560.  Hiortdahlite,  232 
895.  Hisingerite,  246 

History  of  Study  of  Minerals,  198 
894.  Hoeferite,  246 
1 02  2.  Hoernesite,  254 

Holbrook,  44 

Holland,  J.  G.,  33 

Holoaxial,  82 

Homestead,  44 
709.  Homilite,  238 

Hope  diamond,  22 
1009.  Hopeite,  254 
105.  Horbachite,  206 
577.  Hornblende,  153,  232 
296.  Hornstone,  90,  218 

51.  Horsfordite,  204 
671.  Hortonolite,  236 

Hours,  iii 
1138.  Howlite,  262 

225.  Huantajayite,  214 
1271.  Hiibnerite,  270 

837.  Hullite,  244 

691.  Humboldtilite,  238 
1282.  Humboldtine,  272 

732.  Humite,  240 

52.  Huntilite,  204 
1043.  Hureaulite,  256 

Hutchinson,  Charles  F.,  iii 

Huygens,  112 
641.  Hyacinth,  236 
696.  Hyacinth,  238 
319.  Hyalite,  218  « 

500.  Hyalophane,  138,  230 
667.  Hyalosiderite,  236 
620.  Hyalotekite,  234 

Hydrated  sesquioxides,  100 
428.  Hydraulic  limestone,  226 

Hydrous  Sulphates,  264 
1147.  Hydroboracite,  262 

Hydrocarbons,  187 
469.  Hydrocerussite,  228 
1177.  Hydrocyanite,  264 

Hydrofluoric  acid,  81 

Hydrogen,  45 
479.  Hydrogiobertite,  228 
478.  Hydromagnesite,  228 
790.  Hydronephelite,  242 
313.  Hydrophene,  218 
236.  Hydrophilite,  214 
407.  Hydrotalcite,  224 


286 


GUIDE  TO  MINERAL  COLLECTIONS 


Hydrous  carbonates,  228 
Hydrous  chlorides,  214 
Hydrous  oxides,  222 
468.  Hydrozincite,  228 
523.  Hypersthene,  146,  230 

338.  Ice,  220 

418.  Iceland  Spar,  115,  226 

Iddings,  J.  P.,  200 
668.  Iddingsite,  236 
1307.  Idrialite,  274 
1227.  Ihleite,  266 
1203.  Ilesite,  264 
387.  Ilmenorutile,  222 
356.  Ilmenite,  220 
734.  Ilvaite,  240 
874.  Indianai te,  246 
515.  Indianite,  230 
746.  Indicolite,  240 

Indium,  45 
754.  Inesite,  240 
324.  Infusorial  Earth,  220 

Intermediate  plagioclases,  143 

Intermediate  oxides,  220 

Iodine,  45 

231.  lodobromite,  214 
234.  lodyrite,  214 
609.  lolite,  234 

26.  Iridium,  45,  202 

27.  Iridosmine,  202 
32.  Iron,  42,  45,  202 

1045.  Isoclasite,  256 

Isomorphism,  122 
300.  Itacolumite,  218 

371.  Jacobsite,  222 

Jackson,  B.  H.,  200 
Jade,  156 

548.  Jatfeite,  150,  232 
67.  Jalpaite,  204 
168.  Jamesonite,  210 
697.  Jargon,  238 
1258.  Jarosite,  268 


298. 
845- 


Xr,  90,  218 
isite,  244 


541.  Jeffersonite,  232 
1131.  Jeremejevite,  262 
Jersey  County,  40 
1324.  Jet,  274 
1263.  Johannite,  268 

Jo  Daviess  County,  49 
Johannsen,  Albert,  200 
911.  Johnstrupite,  248 
199.  Jordanite,  212 
47.  Joseite,  204 
34.  Josephinite,  202 
Jubilee,  21 


585.  Kaersutite,  234 
1183.  Kainite,  264 
627.  Kaliophilite,  236 
124.  Kallilite,  206 
36.  Kamacite,  202 
1236.  Kamaresite,  266 
826.  Kammererite,  244 

Kaolins,  246 
869.  Kaolinite,  174,  246 

581.  Kataforite,  234 
1085.  Kehoeite,  258 

907.  Keilhauite,  248 
737.  Kentrolite,  240 
145.  Kermesite,  208 
1197.  Kieserite,  264 
204.  Kilbrickenite,  212 
Kimberley,  5 
Kimberlite,  21 
Klaproth,  94 
165.  Klaprotholite,  210 
673.  Knebelite,  238 
916.  Knopite,  248 
1247.  Knoxvillite,  266 
172.  Kobellite,  210 

Kohinoor,  21 
579.  Koksharovite,  232 
23.  Kongsbergite,  202 
1036.  Koninckite,  256 
752.  Kornerupine,  240 
823.  Kotschubeite,  244 
1026.  Kottigite,  256 

Kraus,  E.  H.,  200 
367.  Kreittonite,  222 
263.  Kremersite,  214 
142.  Krennerite,  208 
1229.  Krohnkite,  266 
Kryptom,  45 
Kunz,  G.  F.,  200 

582.  Kupfferite,  234 

512.  Labradorite,  139,  230 
Lacroix,  ix 

1139.  Lagonite,  262 
414.  Lampadite,  224 

1189.  Lanarkite,  264 
763.  Langbanite,  240 

1165.  Langbeinite,  264 

1234.  Langite,  266 
480.  Lansfordite,  228 
476.  Lanthanite,  228 
Lanthanum,  45 

1140.  Larderellite,  262 
947.  Lasurapatite,  252 
772.  Laubanite,  242 
769.  Laumontite,  242 
252.  Laurionite,  214 
126.  Laurite,  206 


GENERAL  INDEX 


287 


1125.  Lautarite,  260 

555.  Lavenite,  232 

533.  Lavrovite,  232 

242.  Lawrencite,  214 

743.  Lawsonite,  240 
Lawyer,  3 

994.  Lazulite,  254 

633.  Lazurite,  236 

20.  Lead,  45,  202 

1179.  Leadhillite,  264 

1195.  Lecontite,  264 

903.  Lederite,  248 
72.  Lehrbachite,  204 

770.  Leonhardite,  242 
1216.  Leonite,  266 

799.  Lepidolite,  172,  242 

808.  Lepidomelane,  244 

Letter  of  transmittal,  v 

543.  Leucaugite,  232 

822.  Leuchtenbergite,  244 

518.  Leucite,  145,  230 
1051.  Leucochalcite,  256 
1304.  Leucopetrite,  274 

607.  Leucophanite,  234 

132.  Leucopyrite,  208 

779.  Levynite,  242 

Lewis,  J.  V.,  200 
1106.  Lewisite,  258 

977.  Libethenite,  252 

486.  Liebigite,  228 
Liebisch,  199 
1323.  Lignite,  192,  274 

901.  Ligurite,  248 

1 86.  Lillianite,  210 

396.  Limonite,  103,  222 
1 19  2.  Linarite,  264 
1114.  Lindackerite,  260 

in.  Linnaeite,  206 
Linnaeus,  198 
1080.  Liroconite,  258 
1063.  Liskeardite,  256 

List  of  Illustrations,  xiii 

942.  Lithiophilite,  252 
Lithium,  45 

427.  Lithographic  Stone,  226 

870.  Lithomarge,  246 

147.  Livingstonite,  210 

131.  Lollingite ,  2  08 
Long  Island,  44 

162.  Lorandite,  210 
1116.  Lossenite,  260 
1214.  Loweite,  266 
1259.  Lowigite,  268 

497.  Loxoclase,  230 
1071.  Ludlamite,  258 
1128.  Ludwigite,  262 

425.  Lumachelle,  226 


1115.  Lunebergite,  260 

Lutecium,  45 
210.  Luzonite,  212 

714.  Mackintoshite,  238 
Macon  County,  40 
Macrodome,  27 
Macropinacoid,  25 
370.  Magnesioferrite,  222 
440.  Magnesite,  120,  226 

Magnesium,  45 
368.  Magnetite,  105,  222 
464.  Malachite,  128,  228 
528.  Malacolite,  230 
1208.  Mallardite,  266 
Malus,  112 
Manebach  Twin,  134 
949.  Manganapatite,  252 
824.  Manganchlorite,  244 

Manganese,  45 
395.  Manganite,  100,  222 

Manganites,  104 
805.  Manganophyllite,  242 
340.  Manganosite,  220 
1004.  Manganostiibite,  254 
130.  Marcasite,  63,  208 
811.  Margarite,  244 
793.  Margarodite,  242 
688.  Marialite,  238 
83.  Marmatite,  206 
851.  Marmolite,  244 
223.  Marshite,  214 
1041.  Martinite,  256 
355.  Martite,  220 
1 1 60.  Mascagnite,  264 
513.  Maskelynite,  230 
817.  Masonite,  244 
1224.  Masrite,  266 
343.  Massicot,  220 
1 60.  Matildite,  210 

250.  Matlockite,  214 
1400.  Maucherite,  208 
1107.  Mauzeliite,  258 
1076.  Mazapilite,  258 

68 1.  Meionite,  238 
652.  Melanite,  236 
603.  Melanocerite,  234 
307.  Melanophlogite,  218 
738.  Melanotekite,  240 

1207.  Melanterite,  266 
690.  Melilite,  238 
608.  Meliphanite,  234 

1283.  Mellite,  272 
109.  Meionite,  206 

251.  Mendipite,  214 
200.  Menenghinite,  212 
317.  Menilite,  218 


288 


GUIDE  TO  MINERAL  COLLECTIONS 


19.  Mercury,  2,  40,  45,  202 
802.  Meroxene,  242 

Merrill,  G.  P.,  200 
442.  Mesitite,  226 
787.  Mesolite,  242 
1015.  Messelite,  254 
85.  Metacinnabarite,  206 
Metallurgist,  4 
Metasilicates,  230 
43.  Metastibnite,  404 
1256.  Metavoltine,  268 
35.  Meteoric  Iron,  202 
Meteorites,  21,  42 
161.  Miargyrite,  210 

Micas,  1 68 

1169.  Michel-levyte,  264 
921.  Microlite,  250 
501.  Microcline,  137,  230 
629.  Microsommite,  236 

Miers,  ix 

232.  Miersite,  214 
956.  Miesite,  252 
489.  Milarite,  230 
314.  Milk  Opal,  218 
281.  Milky  Quartz,  218 

Miller,  W.  H.,  8,  199 
99.  Millerite,  206 

•Millspaugh,  Charles  F.,  iii 
958.  Mimetite,  252 
Miner,  4 

Mineral,  Definition  of,  i 
1316.  Mineral  coal,  274 

Minerals,  Abundance  of,  i 
Minerals,  Numbers  of,  i 
Mineral  production  of  111.,  i 
Minerals,  uses  of,  i,  287 
Minister,  3 
377.  Minium,  222 

Minnesota  Mine,  39 
1196.  Mirabilite,  264 
1187.  Misenite,  264 

Mitscherlich,  199 
1097.  Mixite,  258 
685.  Mizzonite,  238 
Mohs,  199 
Moissan,  199 
Molybdates,  270 
49.  Molybdenite,  204 
Molybdenum,  45 
331.  Molybdite,  220 
1269.  Molybdomenite,  48,  268 
240.  Molysite,  214 
936.  Monazite,  252 
938.  Monimolite,  252 
Monoclinic  axes,  30 
Monoclinic  system,  30,  129 
Monosulphides,  204 


Monoxides,  92 
1265.  Montanite,  268 
669.  Monticellite,  236 
880.  Montmorillonite,  246 
492.  Moonstone,  135 
760.  Mordenite,  240 
1206.  Morenosite,  266 

Morion,  88 
946.  Moroxite,  252 
912.  Mosandrite,  248 
986.  Mottramite,  254 
Moses,  A.  J.,  200 
569.  Mountain  Cork,  156,  232 
568.  Mountain  Leather,  156,  232 

Mukerop,  44 
498.  Murchisonite,  230 
791.  Muscovite,  168,  242 

noi.  Nadorite,  258 
144.  Nagyagite,  208 
417.  Nail-head  Spar,  226 

Names  of  minerals,  196 
222.  Nantokite,  214 
1292.  Napalite,  274 
1233.  Natrochalcite,  266 
784.  Natrolite,  168,  242 
943.  Natrophilite,  252 
473.  Natron,  228 

Natural  gas,  189 

Naumann,  199 
65.  Naumannite,  204 

Neodymium,  45 

Neon,  45 

898.  Neotocite,  246 
623.  Nephelite,  234 
550.  Nephrite,  232 
566.  Nephrite,  156,  232 
914.  Neptunite,  248 
472.  Nesquehonite,  228 

28.  Nevyanskite,  202 
1042.  Newberyite,  256 
878.  Newtonite,  246 
102.  Niccolite,  206 

Nickel,  45 
128.  Nickel-Skutterudite,  208 

Nicol  prism,  115,  129] 
386.  Nigrine,  222 

Niobates,  Tantalates,  175 

1118.  Niter,  260 
Nitrates,  etc.,  260 

1 121.  Nitrobarite,  260 

1119.  Nitrocalcite,  260 
Nitrogen,  45 

1124.  Nitroglauberite,  260 

1 1 20.  Nitromagnesite,  260 
1153.  Nivenite,  262 

258.  Nocerite,  214 


GENERAL  INDEX 


289 


1320.  Non-coking  coal,  274 

891.  Nontronite,  246 
1130.  Nordenskioldine,  262 

751.  Nordmarkite,  240 

462.  Northupite,  226 

632.  Noselite,  236 

957.  Nussierite,  252 

1103.  Ochrolite,  258 
Octahedron,  5 

390.  Octahedrite,  222 

780.  Offretite,  242 

756.  Okenite,  240 
91.  Oldhamite,  206 

509.  Oligoclase,  139,  230 

445.  Oligonite,  226 

976.  Olivenite,  252 

666.  Olivine,  236 

539.  Omphacite,  232 
88.  Onofrite,  206 

292.  Onyx,  90,  218 

430.  Oolite,  226 

308.  Opal,  91,  218 

316.  Opal-agate,  218 

854.  Ophicalcite,  244 
Ordinary  ray,  55 
Organic  acid  salts,  187 
Orloff,  21 
41.  Orpiment,  204 

492.  Orthoclase,  133,  230 
Orthodomes,  129 
Orthopinacoid,  27 
Orthorhombic  system,  25 
Osmium,  45 

818.  Ottrelite,  244 

Owen,  Charles  L.,  iii 
Oxalates,  Mellates,  272 
1281.  Oxammite,  272 
Oxides,  82 
Oxy chlorides,  214 
Oxygen,  45 

789.  Ozarkite,  242 
1287.  Ozocerite,  274 

268.  Pachnolite,  216 
30.  Palladium,  45,  202 
1286.  Paraffin,  274 
798.  Paragonite,  242 
1251.  Paraluminite,  268 
345.  Parameleconite,  220 
Parameters,  8 
Paramorph,  123 
Paramorphism,  123 
580.  Pargasite,  232 
459.  Parisite,  226 

Parsons,  C.  L.,  200 
663.  Partschinite,  236 


683.  Passauite,  238 

Payne,  Edward  W.,  iii 
Peacock  ore,  56 
206.  Pearceite,  212 
320.  Pearl  sinter,  218 
Peary,  R.  E.,  43 
1325.  Peat,  192,  274 
525.  Peckhamite,  230 
552.  Pectolite,  232 
1059.  Peganite,  256 

Penfield,  S.  L.,  200 
254.  Penfieldite,  214 
825.  Penninite,  244 

Pentagonal  dodecahedron,  62 
92.  Pentlandite,  206 
Peoria  County,  40 
Percussion  figure,  169 
249.  Percylite,  214 
339.  Periclase,  220 
507.  Pericline,  141 ;  230 
506.  Peristerite,  230 
915.  Perovskite,  248 
499.  Perthite,  230 
488.  Petalite,  230 

1309.  Petroleum.     Naphtha,  188,  274 
69.  Petzite,  204 
776.  Phacolite,  242 

Pharmacist,  3  ' 
1037.  Pharmacolite,  256 
1070.  Pharmacosiderite,  258 
676.  Phenacite,  238 
1230.  Phillipite,  266 

Phillips,  A.  H.,  200 
765.  Phillipsite,  242 
807.  Phlogopite,  242 
871.  Pholerite,  246 
868.  Pholidolite,  246 
461.  Phosgenite,  226 

Phosphates,  175,  260 
Phosphorescence,  19 
950.  Phosphorite,  252 

Phosphorus,  45 
1031.  Phosphosiderite,  256 
1093.  Phosphuranylite,  258 
820.  Phyllite,  244 
702.  Physalite,  238 
1220.  Pickeringite,  266 
362.  Picotite-Chrome  Spinel,  222 

723.  Picroepidote,  240 
853.  Picrolite,  244 

1218.  Picromerite,  266 
1017,  Picropharmacolite,  254 

724.  Piedmonite,  240 
Pinacoid,  27 

1129.  Pinakiolite,  262 
892.  Pinguite,  246 
797.  Finite,  242 


2  go 


GUIDE  TO  MINERAL  COLLECTIONS 


1142.  Pinnoite,  262 

Pirsson,  L.  V.,  200 
474.  Pirssonite,  228 
1209.  Pisanite,  266 
431.  Pisolite,  155,  226 
443.  Pistomesite,  226 
1154.  Pitchblende,  262 
1310.  Pittasphalt,  274 
mi.  Pitticite,  260 
163.  Plagionite,  210 
290.  Plasma,  218 

Plaster  of  Paris,  182 
25.  Platinum,  41,  45,  202 

Plattner,  199 
388.  Plattnerite,  222 

Pleistocene,  37 
38.  Plessite,  202 

Pliny,  6 1 
1087.  Plumbogummite,  258 

Polar,  68,  93 
384.  Polianite,  222 
519.  Pollucite,  230 
656.  Polyadelphite,  236 
207.  Polyargyrite,  212 
205.  Polybasite,  212 
617.  Polychroilite,  234 
934.  Poly  erase,  250 
106.  Polydymite,  206 
1219.  Polyhalite,  266 
932.  Polymignite,  250 
955.  Polysphaerite,  252 

Pope  County,  79 
1308.  Posepnyte,  274 

Potassium,  45 
1274.  Powellite,  270 

Praeseodymium,  45 
289.  Prase,  218 
309.  Precious  Opal,  218 

Preface,  ix 
728.  Prehnite,  240 

Prism,  27 

828.  Prochlorite,  244 
267.  Prosopite,  216 

Prospector,  4 
190.  Proustite,  68,  212 
84.  Przibramite,  206 
379.  Pseudobrookite,  222 
990.  Pseudomalachite,  254 

Pseudomorph,  123 
827.  Pseudophite,  244 
873.  Pseudosteatite,  246 
410.  Psilomelane,  224 
985.  Psittacinite,  254 
759.  Ptilolite,  240 
940.  Pucherite,  252 
703.  Pyonite,  238 

Pyramid,  25 


612.  Pyrargillite,  234 

189.  Pyrargyrite,  68,  210 

653.  Pyreneite,  236 

116.  Pyrite,  206 

Pyritohedron,  62 

408.  Pyroaurite,  224 

919.  Pyrochlore,  250 

404.  Pyrochroite,  222 

392.  Pyrolusite,  no,  222 

954.  Pyromorphite,  176,  252 

644.  Pyrope,  159,  236 

357.  Pyrophanite,  220 
1008.  Pyrophosphorite,  254 

882.  Pyrophyllite,  246 
I3°S-  Pyroretinite,  274 

680.  Pyrosmalite,  238 

193.  Pyrostilpnite,  212 

526.  Pyroxene,  230 

Pyroxene  group,  145 

922.  Pyrrhite,  250 

104.  Pyrrhotite,  55,  206 

275.  Quartz,  82,  218 

303.  Quartzine,  218 

299.  Quartzite,  90,  218 
1226.  Quenstedtite,  226 
1261.  Quetenite,  268 
Quincy,  124 

Radium,  -45 

1244.  Raimondite,  266 

271.  Ralstonite,  216 

Rammelsberg,  199 
137.  Rammelsbergite,  208 
1276.  Raspite,  270 
170.  Rathite,  210 
614.  Raumite,  234 
40.  Realgar,  204 

353.  Red  Ocherous  hematite,  220 
1016.  Reddingite,  254 
1248.  Redingtonite,  266 

Refraction,  Index  of,  18,  19 
Regent  diamond,  21 
Regular  system,  16 
1278.  Reinite,  270 
482.  Remingtonite,  228 
Rene  Just  Haiiy,  198 
Reniform,  99 
861.  Reneselaerite,  246 
312.  Resin  Opal,  218 

Resins,  187 
848.  Retinalite,  244 
1295.  Retinite,  274 
1002.  Retzian,  254 
150.  Rezbanyite,  210 
1027.  Rhabdophanite,  256 


GENERAL  INDEX 


291 


1096. 

1136, 
447. 
645. 
556. 

496, 
1079. 

575. 
588a, 

913 

194, 


437. 
643 

622, 

1 100, 

1232, 
810, 


553- 
278. 

654- 
713- 

348. 
359- 
426. 
1298. 
843. 

385- 

423- 
136. 
283. 

227. 

535. 
816. 

1210. 


928. 


195- 
191. 

495- 
865. 

347- 


Rhagite,  258 

Radium,  45 

Rhodizite,  262 

Rhodochrosite,  121,  226 

Rhodolite,  236 

Rhodonite,  151,  232 

Rhombohedron,  70,  114 

Rhyacolite,  230 

Richellite,  258 

Richterite,  232 

Riebackite,  234 

Rinkite,  248 

Rittingerite,  212 

Rock,  2 

Rock  Island,  124 

Rock-meal,  226 

Roentgen,  47 

Romanzovite,  236 

Rome  de  L'Isle,  104,  198 

Roeblingite,  234 

Romeite,  258 

Romerite,  266 

Roscoelite,  244 

Rose,  198 

Roselite,  254 

Rosenbuschite,  232 

Rose- quartz,  218 

Rothoffite,  236 

Rowlandite,  238 

Rubidium,  45 

Ruby,  95,  220 

Ruby  Spinel-Magnesia  Spinel,  220 

Ruin-marble,  226 

Rumanite,  274 

Rumpfite,  244 

Ruthenium,  45 

Rutile,  109,  222 

Saccharoidal  limestone,  226 

Safflorite,  208 

Sagenite,  218 

Sal  Ammoniac,  214 

Saline,  44 

Salite,  232 

Salmite,  244 

Salvadorite,  266 

Salt,  76 

Salt,  Origin  of,  77 

Salt  River,  44 

Samarekite,  250 

Samarium,  45 

Sancy,  22 

Sandbergite,  74 

Sanguinite,  212 

Sanidine,  230 

Saponite,  246 

Sapphire,  94,  220 


282.  Sapphire-quartz,  218 
753.  Sapphirine,  240 
689.  Sarcolite,  238 
293.  Sard,  90 

293.  Sardonyx,  90,  218 
Sargasso  Seas,  2 

971.  Sarkinite,  252 
155.  Sartorite,  210 
406.  Sassolite,  224 
420.  Satin  Spar,  226 
1 201.  Satin  Spar,  264 
238.  Scacchite,  214 

Scalenohedrons,  72,  114 
Scandium,  45 
175.  Schapbachite,  210 
1272.  Scheelite,  270 
1284.  Scheererite,  274 
540.  Schefferite,  232 
164.  Schirmerite,  210 
771.  Schneiderite,  242 
662.  Schorlomite,  236 
390.  Schreibersite,  202 
885.  Schrotterite,  246 

6.  Schungite,  202 
256.  Schwartzembergite,  214 
197.  Schwatzite,  74,  212 
786.  Scolecite,  242 
1029.  Scorodite,  256 
718.  Scorza,  238 

Selenium,  45 
1200.  Selenite,  182,  264 
8.  Selensulphur,  202 
241.  Sellaite,  214 
174.  Semseyite,  210 
Senarmont,  47 
327.  Senarmontite,  220 
862.  Sepiolite,  246 
795.  Sericite,  242 
846.  Serpentine,  172,  244 
1238.  Serpierite,  266 

Sesquioxides,  94 
812.  Seybertite,  244 

Shah  of  Persia,  22 
424.  Shell-marble,  226 

Shepardson,  F.  W.,  iii,  v 
444.  Siderite,  120,  226 

Siderolites,  43 
1254.  Sideronatrite,  268 
Silicates,  132 

294.  Siliceous  sinter,  218 
302.  Silicified  wood,  218 

Silicon,  45 

706.  Sillimanite,  238 
17.  Silver,  37,  45,  202 

Sinter,  92 
924.  Sipylite,  250 
29.  Siserskite,  202 


2Q2 


GUIDE  TO  MINERAL  COLLECTIONS 


815.  Sismondine,  244 

127.  Skutterudite,  208 

118.  Smaltite-Chloanthite,  206 

570.  Smaragdite,  232 

875.  Smectite,  246 

448.  Smithsonite,  121,  226 
630.  Sodalite,  236 

1117.  Soda  Niter,  260 
Sodium,  45 
Sohncke,  199 
Sorby,  199 
South  Star,  22 
864.  Spadaite,  246 
1185.  Spangolite,  264 

Spearhead  pyrite,  65 
Specific  gravity,  17 
Specific  heat,  23 
351.  Specular  hematite,  220 

Specularite,  99 
125.  Sperrylite,  206 
647.  Spessartite,  159,  236 
1062.  Sphaerite,  256 

449.  Sphaerocobaltite,  226 
82.  Sphalerite,  52,  206 

900.  Sphene,  248 
446.  Spherosiderite,  226 
358.  Spinel,  104,  220 
Spinel  Twins,  1 7 
902.  Spinthere,  248 
965.  Spodiosite,  252 
546.  Spodumene,  232 
952.  Staffelite,  252 

432.  Stalactites,  116,  226 

433.  Stalagmite,  116,  226 
215.  Stannite,  212 

276.  Star-quartz,  218 
750.  Staurolite,  240 
859.  Steatite,  246 

Steno,  81,  198 
201.  Stephanite,  212 
10420.  Stercorite,  256 

79.  Sternbergite,  204 
334.  Stibiconite,  220 
42.  Stibnite,  46,  204 
767.  Stilbite,  166,  242 

841.  Stilpnomelane,  244 
881.  Stolpenite,  246 

1275.  Stolzite,  270 
383.  Stream  Tin,  222 
605.  Streenstrupine,  234 

1030.  Strengite,  256 

842.  Strigovite,  244 
78.  Stromeyerite,  204 

455.  Strontianite,  126,  226 

Strontium,  45 
1006.  Struvite,  254 
58.  Stutzite,  204 


185.  Stylotypite,  210 
Subsilicates,  240 
Sublimation  deposits,  24 
642.  Succinite,  236 
1294.  Succinite,  274 
1148.  Sulfoborite,  262 

Sulphantimonites,  68 
Sulpharsenates,  212 
Sulpharsenites,  68,  210 
Sulphates,  179 
Sulphides,  46 
Sulphides  of  metals,  204 
1181.  Sulphohalite,  264 
Sulpho-salts,  210 
7.  Sulphur,  24,  45,  202 

Sulphuric  acid,  56,  63 
220.  Sulvanite,  212 
Summary,  194 
154.  Sundtite,  210 
510.  Sunstone,  230 
1 1 80.  Susannite,  264 
1127.  Sussezite,  262 
963.  Svabite,  252 
iii2.  Svanbergite,  260 
108.  Sychnodymite,  206 
141.  Sylvanite,  208 
226.  Sylvite,  76,  214 
Symbol,  8 
Symmetry  axes,  18 
1020.  Symplesite,  254 
999.  Synadelphite,  254 
1213.  Syngenite,  266 
583.  Syntagma tite,  234 
1133.  Szaibelyite,  262 
1198.  Szmikite,  264 

265.  Tachhydrite,  216 

37.  Taenite,  202 

1050.  Tagilite,  256 

858.  Talc,  172,  246 

967.  Talktriplite,  252 

272.  Tallingite,  216 

1 88.  Tapalpite,  210 

926.  Tapiolite,  250 
Tantalum,  45 

978.  Tarbuttite,  254 

452.  Tarnowitzite,  226 

1301.  Tasmanite,  274 

995.  Tavistockite,  254 

1161.  Taylorite,  264 
Tellurates,  268 

330.  Tellurite,  220 

ii.  Tellurium,  45,  202 

483.  Tengerite,  228 

198.  Tennantite,  212 

344.  Tenorite,  220 

674.  Tephroite,  238 


GENERAL  INDEX 


293 


Terbium,  45 

463.  Teschemacherite,  228 
46.  Tetradymite,  204 
195.  Tetrahedrite,  72,  212 
Tetragonal  system,  57 
Tetrahedral  Twins,  13 
Tetrahedron,  13 
Tetrahexahedron,  34 
719.  Thallite,  238 
Thallium,  45 
887.  Thaumasite,  246 
1162.  Thenardite,  264 
471.  Thermonatrite,  228 

Theophrastus,  99 
438.  Thinolite,  226 

Thin  section,  1 29 
269.  Thomsenolite,  216 
788.  Thomsonite,  242 
698.  Thorite,  238 
Thorium,  45 

1158.  Thorogummite,  26*2 
716.  Thulite,  238 
Thulium,  45 
839.  Thuringite,  244 
87.  Tiemannite,  206 
970.  Tilasite,  252 
337.  Tile  ore,  220 
64.  Tilkerodite,  204 
24.  Tin,  45,  202 

Titanates,  248 

659.  Titaniferous  garnet,  236 
899.  Titanite,  248 
Titanium,  45 
904.  Titanomorphite,  248 
701.  Topaz,  162,  238 
649.  Topazolite,  236 
1322.  Torbanite,  274 
1088.  Torbernite,  258 
745.  Tourmaline,  164,  240 

Trapezohedron,  9 
530.  Traversellite,  230 
435.  Travertine,  116,  226 
564.  Tremolite,  153,  232 

Triassic,  21 
1018.  Trichalcite,  254 

Triclinic  system,  139 
304.  Tridymite,  218 
677.  Trimerite,  238 
941.  Triphylite,  252 
966.  Triplite,  252 
968.  Triploidite,  252 
323.  Tripolite,  220 
1 1 03 a.  Trippkeite,  258 
1175.  Tripstone,  264 
1104.  Tripuhyite,  258 

Trisoctahedron,  10 
606.  Tritomite,  234 


1094.  Trogerite,  258 

93.  Troilite,  206 
1068.  Trolleite,  258 
477.  Trona,  228 
909.  Tscheffkinite,  248 

Tschermak,  ix 
1054.  Tyrolite,  256 
244.  Tysonite,  214 
Tungstates,  185 
Tungsten,  45 
332.  Tungstite,  220 
399.  Turgite,  222 
1060.  Turquois,  256 
Tutton,  ix 

1145.  Ulexite,  262 
123.  Ullmannite,  206 
76.  Umangite,  204 

University  of  Chicago  Press,  ix 
571.  Uralite,  232 
Uranates,  177 

1149.  Uraninite,  178,  262 
Uranium,  45 

1150.  Uranniobite,  262 
1159.  Uranosphaerite,  262 

1091.  Uranospinite,  258 

1092.  Uranocircite,  258 
888.  Uranophane,  246 

1264.  Uranopilite,  268 

485.  Uranothallite,  228 
1290.  Urpethite,  274 

Use  of  minerals,  197 
1241.  Utahite,  266 

661.  Uvarovite,  159,  236 

494.  Valencianite,  230 
328. 'Valentinite,  220 
961.  Vanadinite,  252 
Vanadium,  45 
Van  Horn,  F.  R.,  200 
1033.  Variscite,  256 
819.  Venasquite,  244. 
844.  Vermiculite,  244 
693.  Vesuvianite,  238 
1056.  Veszelyite,  256 

Vicinal  faces,  78 
531.  Violan,  230 
1019.  Vivianite,  254 
487.  Voglite,  228 
1052.  Volborthite,  256 
1255.  Voltaite,  268 
146.  Voltzite,  208 

Von  Lang,  146 
1174.  Vulpinite,  264 

411.  Wad,  224 
964.  Wagnerite,  252 


294 


GUIDE  TO  MINERAL  COLLECTIONS 


1095.  Walpurgite,  258 
1039.  Wapplerite,  256 

Ward,  Henry  B.,  iii 
1061.  Wardite,  256 
167.  Warrenite,  210 
1137.  Warwickite,  262 
1057.  Wavellite,  256 
153.  Webnerite,  210 
48.  Wehrlite,  204 

Welcome  Nugget,  35 
764.  Wellsite,  242 
Werner,  199 
682.  Wernerite,  238 

Wherry,  E.  T.,  200 
1280.  Whewellite,  272 
56.  Whitneyite,  204 

Willamette,  44 
675.  Willemite,  238 
122.  Willyamite,  206 

Winchell,  A.  M.,  and  N.  H.,  200 
721.  Withamite,  240 
453-  Witherite,  125,  226 
184.  Wittichenite,  210 
402.  Wocheinite,  222 
554.  Wohlerite,  232 
140.  Wolfachite,  208 
1270.  Wolframite,  185,  270 

Wollaston,  199 
551.  Wollastonite,  232 
318.  Wood  Opal,  218 
1277.  Wulfenite,  186,  270 
97.  Wurtzite,  206 

992.  Xantharsenite,  254 
813.  Xanthophyllite,  244 


400.  Xanthosiderite,  222 
212.  Xanthosonite,  212 
935.  Xenotime,  252 

Yellowstone  National  Park,  24 
Ytterbium,  45 
660.  Yttergranat,  236 
712.  Yttrialite,  238 

Yttrium,  45 
274.  Yttrocerite,  216 
2350.  Yttrofluorite,  214 
1157.  Yttrogummite,  262 
927.  Yttrotantalite,  250 

813.  Zanthophyllite,  244 
481.  Zaratite,  228 
Zeolites,  166 

1035.  Zepharovichite,  256 
1089.  Zeunerite,  258 
1288.  Zietrisikite,  274 

14.  Zinc,  45,  202 
1262.  Zincaluminite,  268 
342.  Zincite,  93,  220 
151.  Zinkenite,  210 
1176.  Zinkosite,  264 
800.  Zinnwaldite,  242 
695.  Zircon,  160,  238 
Zirconium,  45 
Zirkel,  199 
715.  Zoisite,  238 
74.  Zorgite,  204 
637.  Zunyite,  236 


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